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Problem: Furnace main burner ignites, the main burner stays on for 8 to 10 seconds, then shuts right back off

Problem: Your furnace main burner ignites, the main burner stays on for 8 to 10 seconds, then shuts right back off. Your furnace tries this ignition sequence again, and the same thing happens. After 3 times the furnace goes into lock out, and the only way to get it out of lock out is to turn the power switch off and on. Everything starts over again without ignition of your gas burners.

Solution: First, turn off the power to your furnace. Check all wires and ground wires to make sure they have good tight connections and are not burnt. Next, remove the screw or screws that hold your flame sensor in. Please do not confuse the flame sensor with an Ignitor. We do not want to touch the ignitor at all. If you touch an ignitor it will shorten the life of the ignitor or it will break. Below this paragraph we have a picture comparing an ignitor with a flame sensor. Clean your flame sensor with steel wool or emery cloth (fine sand paper). You might need a new flame sensor, but most of the time they can be cleaned and your furnace will work well after cleaning. I have seen flame sensor go out. Most of the time when they go out the white porcelain is cracked. You might want to have a spare flame sensor on hand. Here is a link to our Flame Sensors Page: Please click hear to go to our Flame Sensors Page or you can click on the flame sensor picture below. Near the bottom of this page we have a YouTube video on how to troubleshoot, clean and change-out a flame sensor.

Thanks! We would Love to Have Your Business!

Below is a picture to help you identify what a flame sensor looks like and what an ignitor looks like. Below is a picture comparing flame sensors on the top with an ignitor on the bottom. We do not want to touch the gray glass part of the ignitor or it will shorten the ignitor’s life or it might break.

 

flame sensor
ignitor

Please click here to go to our furnace ignitors page.

Below we have a YouTube Video on how to troubleshoot and clean a flame sensor:


150 thoughts on “Problem: Furnace main burner ignites, the main burner stays on for 8 to 10 seconds, then shuts right back off

  1. You rock ! Good old $5 fix. Worked like a charm. Thanks !!!

    1. Great! Awesome! Glad to hear that you were able to fix your furnace! Thanks for taking your time to let us know that we helped you out. Steve

  2. Hi, I had furnace problem (Trane is my furnace). It was on for few seconds then gas shut off. I put in the new flame sensor, and the problem is still there. Can you help please?

    1. This could be a control board problem, pressure switch problem or a loose wire problem. We discuss this problem on the following page: https://arnoldservice.com/problem-i-purchased-a-flame-sensor-from-you-for-my-goodman-furnace-the-new-flame-sensor-did-not-fix-the-problem-my-furnace-still-lights-for-7-to-10-seconds-and-then-the-gas-goes-out-what-could-be/ I would give the same advice on a Trane furnace or any furnace model where replacing the flame sensor does not fix the problem. I hope you can easily find and fix the problem. If you would like for me to look up parts then please send me your furnace’s model number to our arnoldservice@gmail.com email address. Thanks! Steve

      1. Thanks a bunch for your tip on cleaning the flame sensor — it worked great after I followed your direction. Don from Grand Rapids mi

      2. Thanks so much for your kind words and for taking your time to write us back to tell us the great news! Glad to hear you fixed your furnace! I hope you have a blessed 2017! Steve

  3. I have a similar problem but the symptoms have changed somewhat. My furnace is a Carrier 58SSC110.

    First, early one morning, I noticed that my furnace was not starting, I could hear the inducer start up, shut down, restart, etc. When I checked the furnace I found that the humidifier valve had stuck and water had dripped into the furnace. Maybe a coincidence but I doubt it. OK, the symptom then was just as your describe: inducer starts up, ignitor starts glowing, gas comes on, flame for a few seconds, then it shuts down and starts over. Sounds like the flame sensor right? Later in the day my family tried it again (I had to go to work) and they said it started and ran normally. When I come home in the evening, it is malfunctioning again but the symptoms changed. Now the inducer starts, ignitor glows, but the gas never comes on. I tried activating the valve with a clip lead and the valve itself works OK. Gas came on and was burning normally. (but the blower never started)

    I have power cycled it many times during troubleshooting. The pressure sensor appears to be functioning (closes when the inducer comes on, opens when it turns off) I’m thinking it has to be the control board because it never turns the gas valve on. Probably the flame sensor is still bad (or dirty) also? Is there anything else that could be wrong that would cause the controller to start the cycle (inducer, ignitor) but not activate the gas?

    1. Hi Bob! Sorry to hear that you are having furnace trouble. Yes, this sounds like a control board problem since everything seems to be working accept getting the 24 volts of power sent to open the gas valve. More than likely some water got on the control board and shorted it out. If your furnace control board has a diagnostic flash code then I would suggest trying to read the code. If you would like for me to look up parts please send me your furnace’s product number and I will be glad to look up the control board or any other part you might be interested in. Please send the product number to our arnoldservice@gmail.com email address. I hope you can easily find and fix the problem. Steve

  4. Our furnace keeps lighting the burners for several seconds then shutting them off multiple times (when the fans don’t kick in) then eventually fires up and goes through several heating cycles then back to the cycling of shutting down the burners several times. But, it never shuts down needing to be reset as you described. My landlord won’t do anything about it. My room mate thinks it is dangerous and fears the safety that shuts off the burners will fail and a fire will start. By the way, she took a gas fitter class some years ago and got a C ticket. She wants to blow out the pilot light and just use space heaters.

    What do you think the problem is and is blowing out the pilot light a good idea ti make it safer?

    1. Hi Ms. Myrfield! Sorry that you have to put up with the furnace cycling off and on like this. This has to be worrisome! Sorry that your landlord will not get it fixed! Since you say that your furnace has a pilot light…you probably have a thermocouple that senses the flame of the pilot. We sell thermocouples on the following page: https://arnoldservice.com/product/q340a1090-honeywell-universal-thermocouple/ If the pilot is dirty, burning a yellow flame instead of a blue flame then this could cause the thermocouple to cut the main gas valve off and on like you describe. I would suggest turning off the pilot and cleaning the pilot with a vac or compressed air. If the thermocouple is worn the top layer burnt off then I would suggest a new thermocouple. You can probably purchase thermocouples at Home Depot or your local hardware. Another problem that could cause this cutting off and no could be a loose wire or a thermostat problem. If your thermostat has batteries please make sure they are in good shape. Please make sure all wire connections are tight. I would suggest getting a volt meter set to “Volts AC” and make sure that you are getting a constant 24 to 28 volts between the W and C (com) terminals on your furnace’s control board. If you are not getting the 24 volts between W and C when this going off and on occurs then this shows it could be a thermostat problem or a thermostat wiring problem. I hope you can easily find and fix the problem and then send your Landlord a bill or ask for compensation. God bless you and your room mate. You will be in my prayers to get this fixed. Steve

      1. Steve, Is this furnace problem we have dangerous? Please respond via email if you prefer. My previous question on this has disappeared.

      2. Hi Debbie! Sorry for the slow response we have been helping our son fix up a house where he just moved into. No, this should not be dangerous. I would strongly suggest that you have an HVAC tech check this out. This is very hard on the furnace and gas valve shutting off and on like this. It could become dangerous if the gas valve sticks open and allows gas to build up inside the furnace. I have never heard of a gas valve getting stuck open. I would not like it having the furnace act like this if it was in my home. I would have it fixed. Steve

      3. Thanks again Steve, unfortunately, our landlord has recently padlocked the furnace room on us, so we can’t bring in a man to service it and since he isn’t willing to do it… we can’t get around it.

      4. Hi Debbie! I am so sorry, because I do not know a solution to your problem since you can not get to the thermostat or furnace room! We most certainly do not want to make the Land Lord mad! If this is so bothersome where you can not sleep then I would ask him to please get it fixed and explain you can not sleep with the furnace acting like this. When I do not know what to do I always try to remember to ask God for help. I will pray for you and your room mate that the Land lord will have a change of heart and get your furnace fixed. It is amazing to me how many of my prayers are answered. If you haven’t read this page of mine I hope you have time to read it sometime. God has been so very good and amazing to me in my life that is for sure: https://arnoldservice.com/gods-greatest-gift-us/ You and your room mate will be in my prayers. I hope and pray you get this fixed soon! Steve

  5. Dude, First, you are awesome! Second, I hope you are well. Third, thank you for what you do. Fourth, the problem: I have a very good friend whose furnace is in the same family as the one referenced by MIke T… the model number is exactly the same: Rheem RGDG-07NAUER, and the excellent photos provided by MIke T indicates that it is the exact same unit. As with the furnace of MIke T, it also does not have a flame sensor. You replied to MIke T:

    “If the burners on your furnace are staying on longer than 15 seconds then more than likely the flame sensor is not the problem.”

    This is exactly the condition that my friend’s furnace presents, the main burner flame stays lit after the call for heat for as long as a minute or more, and then extinguishes. As there is no flame sensor on this model, the problem must lie elsewhere. My question to you at this point is, until I get there tomorrow to check, can a blockage in the venting cause this condition, and if so, how might the control board sense this condition? I will check all safety switches tomorrow by removing and shorting their leads. If the main burners, with all safety switch shorted, and the venting disconnected from the furnace, still shuts down after a minute or so, I have no other option than to suspect either the control board or the gas valve, with suspicion, in my mind, lying most heavily on the control board. I will definitely post my findings.

    1. Hi Jack! Thank you so very much for your kind words and question. I would suggest checking all safety controls like the pressure switch, limit and rollouts to make sure they are staying closed when the flame goes out. Also make sure that the thermostat is sending a constant 24 to 28 volts between W and C (com) on the control board when the flames go out. If all these check out OK then like you say about all I can think it would be is the control board. You will probably need a new control board and flame sensor kit. I would need the serial number in order to recommend a control board and flame sensor kit. I hope you can easily find and fix the problem. Steve

      1. Steve, the serial number for this furnace is CM5D302 F0193 3210

      2. Hi Jack! Sorry for the delay in answering you! We have been real busy shipping orders. Our Ruud, Rheem parts program shows that your furnace uses the 62-24084-82 control board that we sell on the following page: https://arnoldservice.com/product/62-24084-82-ruud-rheem-furnace-control-board/ Since your furnace was made the 1st week of 1993 you would need the flame sensor kit we sell on the following page: https://arnoldservice.com/product/62-24044-71-ruud-rheem-furnace-remote-flame-sensor-kit/ I hope you have a nice day! Steve

      3. Steve, the voltage reading between the white t-stat connection and C, ground, went from 28 volts AC to zero when the burner flame died after between 1 and 2 minutes. could you say what the significance of this is? T-stat problem, board problem, or other?

        Thanks,
        Jack

      4. Hi Jack! This sounds like a thermostat problem. You could make sure it is a thermostat problem by taking the thermostat cover plate off and joining the white and red wire together. This should keep the heat on (burners burning) until you separate the red and white wires. If the furnace continues to operate more than 1 to 2 minutes then you have a thermostat problem. I hope you can easily find and fix the problem. Steve

      5. Turns out it was the blower motor. I was so intent on watching action of the burners last night that I completely missed that the blower motor was not kicking in. This caused the main limit control to over heat after a couple of minutes and open, shutting down the burners. The T-stat is a simple two-wire mechanical job.

      6. Great Jack! Glad to hear you found the problem and got it fixed! Awesome! Thanks so much for letting us know!

      7. Steve, the new motor arrived and the furnace is back in good health and everyone is warm. But I am puzzled about something. This furnace has no flame sensor and uses an igniter to light the burner. How does the gas valve know that it is safe to allow the gas to flow to the burner? There is no heat sensor in the vicinity of the igniter. I suspect that the board is programmed to open the gas valve after X number of seconds after voltage is applied to the igniter. But if the igniter is open, and does not heat, how does the board sense this? And if the burner flame is extinguished somehow after ignition, how does the board sense this and shut down the gas valve? Any answers?

        Jack

      8. Hi Jack! Thank you so very much for your business! Glad to hear that you got your furnace fixed and everyone is warm! Awesome! I have seen the setup that you are referring to in many of the older Rheem, Ruud furnaces. They do not have a flame sensor! I really have no idea how the furnace senses the flame other than through the ignitor? I will ask my Rheem Ruud techs this week and let you know what they say. I do know that on most of these older furnaces when the control board goes out which is usually caused by the furnace not sensing the flame they recommend the 62-24084-82 control board with flame sensing kit part number: 62-24044-71. We sell the control board and it has a link to the flame sense kit on the following page: https://arnoldservice.com/product/62-24084-82-ruud-rheem-furnace-control-board/ I will try and get you an answer on this next week and let you know. This has been puzzling to me too. If anyone else knows please feel free to comment. I hope you have a great day and weekend! Steve

  6. Thank you for sharing this. I live in Texas, and we just had our second major cold spell of the season. I have a Rheem Criterion II that I thought was running funny. Upon further investigation it was doing exactly as you described; lighting, running for a few seconds, turning off, and retrying to light.
    I followed the steps you outlined and cleaned the sensor with some #0000 steal wool and it seems to be running perfectly.

    A huge Thank You for taking the time to post this!

    1. Hi Rod! Thanks so much for your kind words and for taking your time to let us know the great news that you were able to fix your furnace by cleaning the flame sensor! I hope you have a Happy, Healthful and Prosperous New Year! Steve

  7. I have a Carrier furnace 58RAV075-101JC that has been troubling for me this winter. Using the great information found on sites like yours I’ve learned a lot and was able to get it working normally but only for this past week. What is happening now is after the call for heat the furnace will burn for several (approx 5)minutes, but will then shut down and lock out when it attempts to relight (and LED indicates lockout). After I reset by taking power down and have the thermostat call for heat, the the inducer fan comes on, glow plug lights bright, and I read with a volt meter that 24 volts is being delivered to the gas valve but get no flame. I can hear a load click at the valve but I know that this is coming from the redundant solenoid. The main solenoid valve is much quieter and so I don’t know if it is opening. I can’t think of any other reason then it is not opening if it is getting the 24 volts but no flame is produced. When I wait several hours, it flames up again and the same process starts over. Any Ideas? Thanks for your attention.

    1. Hi Marvin! I hope that I can help you out. You say that your furnace stops after about 5 minutes of run time, then tries to light and locks out after 3 tries. I would suggest that the next time that your furnace shuts down during a cycle that you test the control board to make sure you are getting a constant 24 volts between W and C (com) from your thermostat. I would also recomment that you check to make sure the limit and pressure switch are staying closed. The CES0110057-02 control board that you have should have a status light on it which should tell you by the number of blinks what has gone wrong. If the furnace is not going off on limit and the pressure switch is staying closed then I would guess that you either have a gas valve problem or a control board problem. The gas valve that your furnace uses is part number EF34CW246. I see that it has a C, P and M connections on the valve. C would be common, P would be pilot valve and M would be main valve. You should be getting 24 to 28 volts AC to the gas valve between C and M (main) when the gas valve should be open. If you aren’t then I would look at your safety controls like the limit and pressure switch or the control board. The gas valve relay on the control board might be going out and acting erratic. I hope you can easily find and fix the problem. Steve

      1. Thank you for your prompt reply Steve. I removed the old gas valve and tested it by applying 24 volts to the C and M connectors and found that the main solenoid will intermittently not open. It appears to be a problem with the connector module itself because if I will wiggle the posts, I can get it to engage. Unfortunately, the connector module on this old valve, 36E36-201, is anchored so that I can’t get at the probably loose solder joints to fix it. Do you have any suggestion on how I can safely remove the manifold from the old valve so I can replace it? It is factory tight and I’m afraid I might damage or bend it by trying to twist it off. I’m wondering if these valves are aluminum(White Rogers won’t reveal), if I heat the valve will it expand more than the iron manifold pipe enabling me to remove it more easily. Any experienced thoughts are very welcome. Marvin

      2. Hi Marvin! I have never tried to repair a gas valve. I would recommend replacing it. I do not have the expertise to repair a gas valve. Here is a link to what I found when I Googled your gas valve part number: https://www.google.com/#q=36e36-201+gas+valve Sorry that I can not make any recommendations for repairing the gas valve. I hope you have a Happy, Healthful and Prosperous New Year! Steve

  8. Thank you for this post. It’s 4:30 in the morning and I just fix my furnace like you showed. Took longer to find a screwdriver than clean the sensor. Thank again.

    1. Hi Jerry! Fantastic! Great! Glad to hear that you were able to fix your furnace by cleaning the flame sensor! Thanks so very much for sharing this! Steve

  9. Found this page last night and followed the instructions. Resolved my issue perfectly. I have heat again. Thank you!

    1. Fantastic! Glad to hear the you were able to fix your furnace! Thanks so much for sharing the great news! Steve

  10. I have a Tran XE78 gas hot air furnace. The unit runs almost a full cycle but the flame turns off the inducer slows down , then it speeds up, the flame turns on again and the cycle continues for approx. 3-5 minutes then turns off? Any ideas? I cleaned the flame sensor already with no improvement.

    1. Hi Mr. Wetherby! Sorry to hear that you are having trouble with your Trane XE78 furnace. It sounds like you either have a control board going out or a draft inducer going out. Please check when the flame goes out the next time to make sure the pressure switch and limit switch are staying closed. You can test these with a meter to make sure they are staying closed (a closed circuit). We have Youtube videos on how to do this on the following page: https://arnoldservice.com/troubleshooting/hvac-troubleshooting-repair-videos/ I do not understand why your draft inducer is speeding up and down unless the control board is turning down the voltage. I would suggest trying to test the voltage going to the draft inducer to see if the voltage varies. Maybe the control board is at fault or the pressure switch is going in and out causing the draft inducer to vary in speed up and down. Please make sure the hole where the pressure switch attaches to the draft inducer is open. You might try sticking a small drill bit through the hole to make sure it is open. Please send me your furnace’s model number if you want me to look up parts at our arnoldservice@gmail.com email address. I hope you can easily find and fix the problem. Steve

      1. Steve,
        I ended up calling the HVAC Co. that I have been using for just a year. I had for the last 20 years using other companies and telling them about my issues. The A coil had never been cleaned. The new Co. owner knew I was frustrated so he brought in an buddy who also works HVAC. They took out the A coil and it was greater then 90% clogged. The clogged surface has a crusty slick surface. It will remain out till spring till can be taken outside to clean. They put the end of the cabinet back. The unit runs awesome now of coarse. The air flow is like we have never experienced. Is cleaning the coil something you do regularly? They HVAC guys even think that the surface may be from the plastic and paper work from when it was installed. They found pieces of metal from when it was installed .

      2. Hi Mr. Wetherby! Glad to hear that your service techs were able to find and fix your problem! We cover this problem on the following page: https://arnoldservice.com/problem-why-does-my-furnace-air-conditioner-have-poor-air-flow/ and on the following page: https://arnoldservice.com/problem-what-could-be-causing-my-indoor-coil-to-freeze-up/ When I was doing HVAC service and on what I call “Furnace Clean and Check” service calls, I would always pull out the blower assembly, lay on my back with a flashlight and look up into the furnace beyond the heat exchanger to see if the AC evaporator coil was dirty and needed cleaning. This was the quickest way for me to inspect the AC coil while I had the blower out and I was going to clean and blow out the blower anyway. If the AC coil needed cleaning then I would take the sheet metal door off the coil and clean with a wet vac, coil cleaner, water sprayer and fin comb. I would not reinstall the blower assembly until the coil was cleaned because water and coil cleaner can drop down on the blower motor and mess it up if the blower is in place. Yes, every time you have your furnace cleaned and checked the service company should inspect the AC coil (evaportator coil) bottom to make sure it is clean and not stopped up. Most companies do not want to do this because it is time consuming taking the blower out and even more time consuming to clean the evaporator coil. As you say it makes a big difference in air flow after a coil is clean and it will make a big difference in you heating and air conditioning utility bill! Thank so much for sharing your experience and solution to your furnace problem. Hope you have a great day! Steve

    2. Just pulled flame sensor our sanded it down reinstalled and furnace function is perfect , thank you so much

      1. Hi Greg! Great! Fantastic! Glad to hear that you were able to fix your furnace by cleaning the flame sensor! Thanks so much for sharing and letting us know the great news! Steve

  11. Mr. Arnold,
    I’ve found your article and comments informative and commend you for helping your readers. Unfortunately I have not run into the situation I’m experiencing. Have a Bryant, Day & Night, Payne, Plus 90, Model 399AAZ048080. It’s like a temperamental soul. Will run on schedule, then not at all. Have to prompt it by turning off the switch,then on, to get it going. But no guarantee it will stay on programmed schedule. Nor will it run to programmed temperature. Had it set for 68 but it may shut itself off at 64. Have changed the thermostat and circuit board but it still has a mind of it’s own. Any insights other than an exorcism?
    As another point of curiosity, what are the symptoms of a cracked or failed heat exchanger.

    1. Hi Mike! From looking at some of the parts on your furnace I see that you have the LH680005 3 wire pilot burner. Please make sure this pilot burner is clean. If you can blow the 3 wire pilot out and clean it with compressed air I would suggest doing this. If the pilot flame is not hitting the sensing plate on the pilot burner with a good blue flame then this will cut the gas off to your furnace because the control board senses there is no pilot burning. A cracked or leaking heat exchange would cause the pilot flame to blow or move away from the sensing plate. I would like to suggest that your watch the pilot flame when your blower starts. If the flame on the pilot begins to move around when the blower comes on then it is a good possibility that you have a leaking heat exchanger. Another sign of a leaking heat exchanger would be the burner flame changes colors and moves when the blower starts up, fire or heat come out of the front of the furnace when the blower starts or if the auxiilary limit trips when the blower comes on. This problem could also be caused by a erratic control board or thermostat problem. We have a troubleshooting flow chart that I hope will help you out: https://arnoldservice.com/furnace-trouble-shooting-flow-chart/ If you want me to look up parts then please contact me through our arnoldservice@gmail.com email address. Parts lists are to big to show on the posts. I hope you can easily find and fix the problem. Steve

  12. Hello- I have Trane XR80, and the furnace will not stay on. I seen the red light flashes four times, so i bought a new high limit switch and replace it, then i tried again and still give me the same thing with four times red flash. I checked almost everything, the only thing i did not find is a filter , but I have two grills in the ceiling in my living room, so i changes those filters with the same results. please what to do next?

    1. Hi Maen! I assume the 4 flashes mean the the furnace has gone off on limit. I would suggest that you use a volt meter to test the limit and rollout switches (if you have any) to make sure they are all closed. If all the rollouts and limit are closed then you might need a new control board. Please make sure the 4 flashes mean an open limit. I am not a Trane dealer so I do not know what the 4 flashes mean. Most of the time the control board is right in showing what is actually wrong with a furnace. I hope you can easily find and fix the problem. Steve

      1. Steve, I have a VERY old Montgomery Ward gas furnace. Yes, Montgomery Ward!
        It has been a work horse for ever but over the past 5 years we’ve noticed that if the furnace is turned off for a longer period of time without kicking on… say over 4 hours… sometimes it will turn on the gas and flames, stay on for a anywhere from 7 seconds to 45 seconds then kick off. The fan turns on at around 15 seconds (if the flames are still active) but like I said, sometimes the flames will kick off at 40-45 seconds when the fans already running… then when the flames turn off so does the fan immediately.

        There is no flame sensor in this unit… as this unit is so old it’s basically a mini circuit boards to connect the wires to for the thermostat, which then go to the gas valve and thats it. Other then the thermocoupler keeping the pilot light active (Pilot light has not gone out in a decade at least).

        There are new filters (it takes 2 and sits at a V) but it did not change anything.
        It WILL eventually kick on and stay on then keep active at temp… but it’s always doing this after sitting for a few hours, I guess it cools down to much? I’m not sure because there are no sensors anywhere on this thing! No pressure sensor or anything.
        Thoughts?
        Thanks!

      2. Hi Tim! It is remarkable that you can still use this old Montgomery Ward furnace! The good thing is that it is not complex with circuit boards and electronics like the new furnaces. The bad is that it probably is not too efficient. I would start by troubleshooting the furnace when it is cold, since you say this is when the problem occurs most often. I would first take a look at the lighting of the burners to see if upon ignition the flame of the burners rob the flame on the pilot thermocouple. If the flame is moving away from the pilot thermocouple upon ignition I would suggest cleaning the burners, pilot and thermocouple. If you have an air compressor I usually take the pilot and burners outside and blow them out with compressed air. I would suggest replacing the thermocouple since it is 10 years old while you have the pilot assembly out. I would also suggest testing with a volt meter set to volts AC on the “W” and “C” terminals on the control board to make sure the thermostat is supplying a constant 24 to 28 volts to the gas valve when this going off occurs. Also check and see if the gas valve is getting a constant 24 to 28 volts to keep it open during this on/off problem. If the gas valve is getting a constant 24 volts to stay open from the thermostat and still going off and on erratic then you either have a gas valve problem or a thermocouple flame sensing problem. I hope you can easily find and fix the problem. Steve

  13. I have a problem with my campers furnace. Sometimes it starts and cycles through 3 times then locks out, and others it comes on lights fine, and has sporadic cycles. Sporadic as in it’ll heat the camper until it’s toasty, flame goes out and the blowers only going, and before the blower shuts off the flame reignites and continues blowing. We have had an “RV Doctor” come look at it and he says that the lines are fine, no leaks, but that the mechanism that some mechanism is getting to hot so it’ll shut off for safety reasons. He installed something that would give it about a 5 degree increased the but idk. We have had to resort to using a kerosene heater from time to time. Any info would be appreciated. Me and my family are forced to live through a Maine winter inside this camper. Anyways take care and God bless.

    1. Hi Jon! It sounds like your RV furnace is going off on high limit which means it is over-heating. This could be attributed to poor air flow or too much gas input pressure (burners are burning too hot and putting out too much heat for your furnace’s air flow). We discuss poor air flow problems on the following page: https://arnoldservice.com/problem-why-does-my-furnace-air-conditioner-have-poor-air-flow/ We have lots of troubleshooting advice with videos on the following page: https://arnoldservice.com/troubleshooting/ I hope you can easily find and fix the problem. Steve

  14. My problem is
    -The light on the furnace dose not blink. It stays red.
    -When I turn the furnace on the fire comes on and then the fire goes out. I cleaned the heat sensor. This dose not work. All the videos I watch states that once you clean the heat sensor the furnace should start to work again. But in my case it dose not work.

    1. Hi Ari! You might have a loose wire connection some where or you might need a new flame sensor or control board. Please make sure the flame sensor is sitting in a good hot blue flame when the gas does come on. If it is not sitting in a good blue hot flame then you might need to clean the burners. I would look for loose wires first by turning the power off to the furnace then checking to make sure all wire connections are tight. Please make sure your ground connections are tight. If this does not work I would try a new flame sensor and if this does not work then a new control board. I hope you can easily find and fix the problem. Steve

  15. Hi guys, I just want to thank you for this post, you save me at 3 AM in a 35* night with a 7 months old baby at home. Blessings

    1. Awesome! Fantastic! I am so very glad to hear that you were able to fix your furnace and keep your family warm!!! Thank you so very much for sharing this and letting us know! You brightened our day and made our day great! I hope you have a bless Holiday Season! Steve

    2. Hello Mr. Arnold,

      I have a York Affinity furnace (about 7-8 yrs old). Just this year I noticed the furnace was not reaching the temp I set. It just tried to power up, and after about three cycles it just shuts down. I tried cleaning the flame sensor several times, but that didn’t work. Finally I decided to buy a new flame sensor, but unfortunately, that also didn’t work. Can you give me some advice? Would really appreciate it because it’s starting to get really chilly now. Thanks!

      1. Hi Jeff! Sorry you are having trouble with your York furnace. We cover the question you asked in detail on the following page: https://arnoldservice.com/problem-i-purchased-a-flame-sensor-from-you-for-my-goodman-furnace-the-new-flame-sensor-did-not-fix-the-problem-my-furnace-still-lights-for-7-to-10-seconds-and-then-the-gas-goes-out-what-could-be/ I hope this helps you find and fix the problem. Steve

  16. What’s the effects if a high limit is bad? Ohm it out and it reads good! But I also know if the blower doesn’t come on ( I replaced about 4 months ago) it can give the high limit power to ignite and senses no flame and it will tell the board I have a bad limit… pleases give your insights

    1. If the limit is bad the furnace will not ignite. It will not allow the gas valve to open or the ignitor to glow. If the limit ohms out OK then the limit is not bad. I would test the limit during a heating cycle. You should get 24 volts AC from each side (each wire) to ground. If one side does not get 24 volts then the limit is open and you either have a bad limit or a furnace over-heating problem. I hope you can easily find the problem. Steve

  17. Hi Steve – My 25-year-old Goodman furnace was shutting off just a few seconds after ignition, and after some online research I suspected a flame sensor problem. Because of the age of the furnace I decided to just replace the entire sensor/igniter/pilot unit rather than try to clean the sensor. Here’s a link to the part I bought if that helps: http://www.hvacpartsusa.com/index.php?route=product/product&product_id=8228.
    After installing the new part the furnace is working beautifully (for several days now). BUT . . . I notice the flame sensor sits in the path of the burner flames and stays red hot while the furnace is on. Is this normal? I somehow assumed that the flame sensor was only there to detect a flame from the pilot, but perhaps I am wrong, and I never really looked when the furnace was operating normally in the past. The installation of the new part was all according to pre-drilled holes so I don’t see how I could have misplaced it. Again, everything is working great but I just want to be sure I don’t burn out my flame sensor prematurely. Thank you. You are operating a very generous advice column here and I definitely will look to Arnold’s for repair parts in the future.
    Patrick

    1. Hi Patrick! Thanks so much for your kind words and the question. I see that you purchased a Honeywell SmartValve pilot burner assembly which is great. We sell one on the following page: https://arnoldservice.com/product/70l5401-honeywell-smart-valve-complete-pilot-burner-assembly/ Probably the search engines did not pick our site up. Lol I have seen some of these installed on working furnaces and yes some do sit in the flame and get red hot. Especially the curved metal part that looks like a fork on top. I would say this is normal because the pilot has a screw hole and a protruding small locator that sticks out on the pilot assembly so it is hard to install the part in the wrong place. I hope you have a great day and week! Steve

  18. Thank you so much for this post! Took me 5 minutes and my furnace was fixed. God bless you for taking time to post this video and explanation. You just saved my family a chunk of money.

    1. Hi Mr. Johnson! Great to hear that you fixed your furnace! Thanks so much for letting us know the great news! God bless you and your family today and always! Steve

  19. My furnace goes on light then lights the other part and shuts off . It’s not the flame sensor and the green board got replace but that isn’t the problem. I’ve had furnace people here for two days now and they still don’t know whats wrong with it and it is cool please help.

    1. Hi Sarah! So sorry to hear that you are having trouble with your furnace! This sounds like a flame sensing problem. Please make sure all wire connections are good and tight especially your furnace’s ground wires (the bare copper wire and white nuetral wire). Please make sure the flame sensor is sitting in a good hot blue flame the little time that the gas is on. Maybe you received a bad flame sensor or control board. Please make sure the pressure switch is staying closed the whole time the draft inducer is running. I have seen pressure switches open up when the gas comes on and this was a problem in some furnaces. Please make sure the opening in the draft inducer where the pressure switch tubing attaches is open. You might want to stick a hard wire or a drill bit in the hole of the draft inducer to make sure it is open. Sorry that I can not be of more help. Best of luck in finding and fixing the problem. Steve

      1. I had this problem with a Rudd Weatherking. I too changed the flame sensor (twice thinking I had gotten a defective one) and the ignition control board. What I found was that that the “polarity” of the AC line in has to be correct. I have been an electronics engineer and Master Electrician for 25 years and this is the first time that I have seen something that the “polarity” actually mattered on AC, so I post this hoping it will help others, since the post above says the service techs didn’t know what was going on. I can’t explain it, but apparently on the ICB there is evidently a reference between the neutral and ground and if the neutral and hot (common) are not connected as labeled the flame sense circuit will register about 30uA instead of the 300uA on the flame sensor. Again, I hope this helps some out there with the same problem and it won’t take them 2 weeks to get it corrected like it did me.

      2. Hi Mr. Horning! Thank you so very much for taking your time to post this information about the “polarity” having to be correct on Ruud, Rheem and Weatherking furnaces for the flame sensor to work properly. I am sure this will help others solve their furnace problems. I really appreciate your time for posting this! Hope you have a Great and Blessed Holiday Season!

  20. I have replaced my flame sensor. I don’t think it was ever changed in 18 years. I cleaned the air filters, I have metal ones they were not dirty, but I cleaned them. Previously before replacing the flame sensor the furnace would heat the house and the fan would not turn off. I found out that if I kept the temp at 64 the fans would turn off once it heated the house to temp. Then it would not stay lit. So now we are back to the start. Changed the flame sensor but the fans still will not turn off so I have to then turn the main switch off. Also, it seems as though it does not want to heat past 67. But now the furnace will not stay lit again. I have a trane ex90. The flame sensor doesn’t seem like it could not be in the right space because it’s locked in place with the hex bolt not a screw. Could I just have a bad flame sensor? Would a bad thermostat be the problem with it not lighting, or the fans for not kicking off? I think I got everything.

    1. Hi Ashely! Sorry to hear you are having problems with your furnace staying lit and the fan not turning off. If the limit switch is bad or if the furnace is going off on high limit then the fan will run because the control board thinks the furnace has over heated. You will need a volt meter to do some testing. I would suggest testing to make sure the limit is not open. We have a limit testing video on the following page: https://arnoldservice.com/gas-furnace-limit-control-video/ You should make sure that the flame sensor is sitting in a nice hot blue flame when the burner ignite. If it is not sitting in a blue flame then your burners might need cleaning or gas valve pressure might be adjusting. Yes, the thermostat or a stuck relay on the control board can cause the fan to run all the time. I would suggest testing with a volt meter between G and C (com) if you are getting 24 volts between these two terminals then the thermostat is sending 24 volts to the furnace telling it to keep the blower on. You might need a new thermostat. If you are not getting 24 volts AC between C and G then you might have an open limit on the furnace or a stuck relay on the control board. If you want me to look up parts please send me your furnace’s model number at our arnoldservice@gmail.com email address. I hope you can easily find and fix the problem. Steve

  21. Steve Arnold, WOW!!! I’ve been trying for weeks to get someone over here to solve this problem. In less then ten minutes watching your video & going downstairs. The problem is solved. I can’t thank you enough.

    1. Hi Michael! Great! Awesome! I am so glad to hear that you were able to fix your furnace! Thank you so much for sharing your experience! Steve

  22. Hi, I have a BDP/Carrier furnace from 1987. The burners will light and run for about a minute or two, but within a minute after the blower turns on the burners and pilot go out. If I remove the cover to the blowers the burners will stay on and heat the house. I checked to make sure the air intake vents in the house are not covered. Any suggestions?

    1. Hi Darren! Great question! This sounds like the furnace is probably over-heating and going off on limit. I would suggest that the next time the furnace gas goes off prematurely that you check the limit with a volt meter to see if the limit is the problem. You might need a new limit or more than likely the limit is doing its job by cutting off the furnace to keep the furnace from getting too hot. Over-heating of the furnace can be caused by as you have already checked some of the registers being blocked or turned off. Over heating of the furnace can also be caused by a dirty filter, dirty blower wheel, slow blower motor, (might need a new capacitor) stopped up or blocked air conditioner evaporator coil or the gas valve gas pressure being set too high. I would suggest checking the easy causes first like the filter, dirty blower wheel or have the capacitor on the blower motor checked. Best of luck in finding and fixing this problem.

      1. My HVAC unit had the same problem. I checked the and changed the filter. Changed the flame sensor. I watched a video on the sequences of events that need to happen for the unit to work. The video explain what all needs to happen and where all the parts are located and their functions. What it came down to is the day before I had a new roof put on my house. Debris had fallen down the exhaust duct and had gotten into my combustion air blower. This would allow the heat- exchanger to over heat. I took the exhaust pipe off and clean it and also took the combustion air blower off and clean it out. It now works properly . Hope the info was helpful.

      2. Hi Mr. Gowen! Thank you so much for sharing this information about debris falling down into the vent and draft inducer after a roof installation. I am sure this with help other people. Steve

  23. We have a Bryant plus 80 furnace. We replaced the ignotor and the flame sensor. We reset it and start it, the ignotor glows then you hear the gas click on, and then the flames won’t light. Every once in a while it will kick on, but rarely. Any other things to try to fix this or is it time to call a tech?

    1. Hi Jeff! Sorry to hear you are having trouble with your furnace lighting. It sounds like the ignitor is OK because it is glowing. Sounds like probably either the burners are dirty or you are not getting enough gas pressure to light the furnace. If the ignitor is glowing bright and the ignitor is positioned correctly, then the furnace burners should ignite if the gas pressure is enough. Gas pressure adjustments can be dangerous and I would recommend that you get a tech to do this. You might try cleaning the burners with compressed air and a vac before calling a tech. I hope the cleaning will solve your problem. If you want to try and adjust the gas pressure up, there are several YouTube videos on how to do this. Here is a link: https://www.google.com/#q=how+to+adjustment+gas+pressure+on+a+gas+furnace I hope you can easily get it fixed. Steve

  24. BEFORE finding this site, I cleaned what I thought was the flame sensor but it was the igniter. (WHOOPS!) So you know I had to replace it since it crapped out. Now that I cleaned the flame sensor, replaced the igniter, blew on some hoses, made sure that all of the connections were tight and nothing was loose the furnace cycles through trying to turn on the burners. The burners go on for about 8-10 seconds then the furnace goes back to cycling thru igniting the sensors. sometimes it is successful in turning on the burners for a cycle but the second time around it goes back to being unable to light the burners. The indicator light is steady and per the panel that means that everything is operating normally. What else should I try? I’m at my wits end and I dont want to call a service person out here.

    1. Hi Eylin! Sorry to hear you are having trouble with your furnace burners staying on. I would suggest making sure the flame sensor is sitting in a good hot blue flame when the burners light. If the flame sensor is positioned out of the flame or not in a good blue flame it will cut the gas valve back off like your describe. I would suggest that you turn off the power to the furnace and clean the burners out with a vac or take the burners out and clean them with compressed air. Sometimes cleaning the flame sensor does not work and you might need to get a new flame sensor. If a new flame sensor does not work then you might need a new control board. If you want me to try and look up parts please send me a furnace model number and I will try to look the parts up for you. I hope you can easily find and fix the problem. Steve

  25. Dear Mr. Arnold,
    It is Thanksgiving and our furnace was not working. I went into the crawl space and saw that the burner was on and then off and again and then quit. I found your video online, got a crisp one dollar bill, cleaned it off and we now have heat for Thanksgiving. We are very thankful for you to have made this post and video. I hope that you have a wonderful Thanksgiving yourself.
    Bob.

    1. Hi Mr. Kessler! Awesome! so very glad to hear that you fixed your furnace by cleaning the flame sensor! Thanks so much for your kind words and for letting us know! You have made my Thanksgiving lots brighter!

  26. Thanks for this great advice. My furnace is doing this exact same thing, but the flame in the main burner only stays on for 3-4 seconds. My flame sensor is in the 4th burner, furthest away from the main burner with the igniter. Since it never lights all burners during its “test burn” how is the flame sensor in play? This is a 25-year-old Carrier furnace. Thank you for any help you can offer.

    1. Hi! Please check and make sure all the burners are clean and a good blue flame is hitting the flame sensor when the burners ignite. I would suggest checking all connections to make sure they are good and tight, especially the ground wire connection. If the burners are not lighting all the way across after the cleaning, then you might need to adjust the gas pressure up on the gas valve. This can be dangerous so you might want to call in a professional. If all this does not work then you might have a control board problem. I hope you can find a simple solution. Hope you have a great day and week! Steve

  27. I just found your advice page this morning. Wow, you are a charm. I’m tracking down my old Trane’s burner shut-down “No-flame” problem. Just from reading the posts and your helpful replies I am so impressed with your helpfulness. I’ll run through a few of the troubleshooting steps and see how I do before bothering you for specific advice. Thanks for caring about your fellow man, and for being so sharing with your knowledge and experience.

    1. Hi Mr. Day! Thank you so very much for your kind words and comments! I hope the troubleshooting tips will help you find and fix your heating problem. Hope you have a great day and weekend! Steve

    2. Hello, I have a furnace problem I need some help with. I have a 5 year old nordyne that lights but goes out the second the blower comes on (prematurely). I just had a metal roof over added this summer and thought it may be an airflow problem like CO2 smothering the fire due to lack of fresh air so I slid the outer pipe up about 5 inches so the furnace could pull air from inside. Still the flame goes out. Have had to HVAC repairmen out and they are baffled, too. I hope some one has an answer for me. Thanks

      1. Hi Donna! This is one of those problems where you would need to be there and testing with a volt meter when the problem occurs. This sounds like either a flame sensing problem or a pressure switch problem. I would suggest making sure all wire connections are tight. Make sure the flame sensor is sitting in a good hot blue flame. I would suggest testing the pressure switch when the problem occurs to make sure the pressure switch is staying closed when the blower comes on. I have seen pressure switches open up in the slightest difference in air pressure. Please make sure the blower compartment is not open to draw air around the furnace. The return air and supply air should be sealed so it is not drawing air where the furnace is located. If you have a condensing furnace please make sure the condensate drain is open and water can flow free. A stopped up condensate drain or partially stopped up pressure switch tube/draft inducer can cause pressure switch problems. Best of luck in finding and fixing the problem. Steve

  28. We recently had two hvac guys from different companies tell us the inducer was bad on our furnace. We got it replaced and it still didn’t fix the problem. The hot air will blow for a while and then it just stops and blows our room temp air. Any idea what the problem could be?

    1. Hi Mr. Sanders! This sounds like either a furnace limit or the flame sensor is kicking the flame out. Does your flame run very long? If it lasts longer than 8 to 10 seconds then I would recommend checking the furnace limit with a volt meter. If the flame cuts off in less than 8 or 10 seconds then I would suggest cleaning the flame sensor and check to make sure all connections are good and tight. Please check all connection on your furnace. Sometimes connections will vibrate loose. We have lots of troubleshooting advice on the following page: https://arnoldservice.com/troubleshooting/ I hope you can easily find and fix the problem. Steve

  29. I have a Coleman Furnace that is short cycling. Its 30 years old so no computers and circuit boards. The blower will run a couple of minutes than stop, meanwhile the flame never stops. This rules out the limit switch and relay, so I swapped out the fan switch to no avail. I also replaced the limit switch relay for S and G’s. No better. The furnace is hot and blows hot air for 2 – 4 minutes then the blower motor shuts down. New motor and capacitor btw. I turn the blower on from the thermostat and it runs no problem blowing warm air. New filters every 3 months. I love this old unit because i can usually fix any problem but right now i am stumped… Any suggestions besides the heat exchanger?

    1. Hi Brando! Either some control which controls the fan motor is cutting the fan motor off after 2 to 4 minutes or you have a motor speed that is going out and the motor itself is shutting off because of the motor windings being weak. I would suggest checking with a volt meter to see if the motor is getting voltage (110 to 125 volts) when the motor stops. If the motor is getting 110 to 125 volts and not running then you have a motor problem. If the motor is not getting 110 volts then you have a motor fan relay problem. This should not be hard to find the problem using a volt meter. Best of luck in finding and fixing the problem. Steve

  30. My uncle has a moffat natural gas furnace and it’s fairly old. The gas line was changed this summer and since the weather has cooled off he has noticed he can’t start it anymore. The pilot will light and stay lit as long as you leave it. When the main burners are turned on they will burn while slowly dying down for 30 seconds. Then a click is heard, the main burners die and the pilot light goes out too. Recently changed limit/ fan switch with no difference. Also changed the thermocouple. Any thoughts ?

    1. Hi Logan! This sounds like a gas valve problem. Maybe the gas valve is partially stopped up since you say the gas line was changed this summer. If this was the main gas line, then you might have some air in the gas line. The people who changed the gas line out should have bled the air out. You might need a gas valve pressure adjustment to get more gas to the burners. The screen on the gas valve might be partially stopped up. I would suggest turning off the gas and inspecting the gas valve to see if the inlet screen is stopped up inside the gas valve. Best of luck in finding and fixing the problem. Steve

  31. i have a goodman gas furnace about 12 years old…if i remove the panel that covers the bunner and the gas valve..my unit will run and heat my house as it should…if i install the panel it will kick on heat for a few minunts then the heat will kick off,new heat sensor,gas valve….and it is giving me …7…red flashe’s.., gas valves are pretty old…maybe…25…r…30.years old…i will replace them..

    1. Hi Mr. Billiot! Please try to read on the furnace door and see what the 7 red flashes mean. There should be a blink code on one of the furnace doors. This sounds like a pressure switch problem or you might have something partially stopping up your vent. A partially clogged furnace drain condensate line will cause this problem too. I would suggest checking your pressure switch with a volt meter set to volts AC when the gas goes off. Check to make sure the pressure switch is staying closed. If the pressure switch is opening up during the cycle with the panel installed, then I would suggest checking your vent system and furnace condensate drain (if applicable). I hope you can easily find and fix the problem. Steve

  32. We have s carrier furnace and over the summer has our gas line regulator replaced outside. When we went to fire up the furnace this fall the igniter would glow, and we would get a flame on the main burner on the right of the box but the rest of the burners wouldn’t ignite. They do ignite occasionally when we try it but not every time. We cleaned the flame sensor, but that is on the far left of the box away from the main burner. I’m not sure if the problem is the flame sensor or not, since it is on the opposite side from the main burner, or if the problem lies in the fact that the other burners don’t turn on once the main one does. Considering replacing the flame sensor but would have to have it shipped so looking for opinions first.

    1. Hi Erin! This sounds like an LP gas (if you have LP gas) or natural gas pressure problem. Since you said that the gas line regulator was replaced this summer more than likely the pressure going to the gas valve is not set correctly either on the outside regulator or the furnace’s gas valve’s regulator. Perhaps the gas company let some rust or dirt into your gas line and it partially stopping up your gas valve. Maybe they adjusted the pressure too high and the wrong gas/air mixture causes your furnace to burn with only one or two burners lite. I would suggest first that you turn the gas off to the furnace and clean your burners out with compressed air or a vac, if you do not have an air compressor. This will make sure that the burners are clean and this problem is not being caused by dirty gas burners. I would suggest that you either call the gas company back out who replaced the regulator and ask that they adjust the regulator or call an HVAC company to make sure the gas pressure is set correctly for your furnace. More than likely it is not a flame sensor problem, but a gas pressure problem. I hope you can easily find and fix this problem. Steve

  33. I have a gas furnace and the ignition lights up stays on for 3seconds and flame goes out replaced flame sensor does same thing

    1. Hi Mr. Wade! Since you are still having problems after replacing the flame sensor I would suggest that you check all wire connections and ground connections to make sure they are good, tight and not burnt. Please make sure your pressure switch is staying closed when the draft inducer is on. I have seen furnaces where the pressure switch opens up shortly after the gas on the furnace ignites. I would suggest testing to make sure all your rollouts and limit is staying closed all the time. You might try another flame sensor just to make sure you are not installing another bad flame sensor. If you do not find the problem, or if this does not fix the problem then I would suggest a new control board. Please send me your furnace’s model number if you would like for me to look up parts. Best of luck in finding and fixing the problem. Steve

  34. Hi Steve.

    We have a 10 year old Pennco model 15045 Series boiler. It provides supplemental baseboard heat to our basement. The boiler has an intermittent (spark) type pilot ignition system, a UT 1003-600A controller and a Honeywell VR8204H1006 valve.

    The problem started about a month ago. When the thermostat calls for heat, the igniter sparks and the pilot ignites after a second or two. The main burners ignite for several seconds before the main and pilot valves drop out.

    Thinking bad flame sensor I replaced the combined pilot / igniter / sense unit.
    The problem persisted.
    I discovered the problem is with the pilot flame not reaching the flame sense after main burner ignition – and – it happens only when the inspection covers are in place. If I remove the inspection covers the pilot remains lit and the boiler will run until the thermostat stops calling for heat.

    Further investigation shows that the with inspection covers in place, the majority of the combustion air enters the firebox through an opening in the lower right corner of the inspection plate. This opening is used for the blowback switch. The concentrated air flow through this opening is enough to pull the pilot flame away from the sense probe. The pilot appears to remain lit on the opposite side (the main burner side). The controller, sensing loss of pilot, shuts off the main and pilot valves.

    Thoughts?

    1. Hi Pat! I am sorry, I am not very familiar with boilers. If the flame on the pilot is being blown off target I would like to suggest that you clean the heat exchanger and vent to make sure the heat exchanger and vent or unobstructed. Please make sure the boiler is venting properly. I know that a stopped up or leaking heat exchanger will cause the furnace burners to light properly then after 5 or so seconds the burners will start burning back (not burning at all on part of the burner) causing raw gas to enter the heat exchanger, soot the heat exchanger up and cause more restriction in the venting of the furnace. The pilot should burn straight up if the vent and heat exchanger are not blocked. Best of luck in finding and correcting the problem. Steve

  35. My gas furnace (don’t know make/model… i’m at work!) has been having cycling issues, and three repair techs later, I am told that it needs a new circuit board, or I need to replace the entire system. I am curious because the first tech did some routine maintenance (change the filter, cleaned the flame ignitor), tested the voltage, temperature of the air flow, and then he skipped off with my $104 “diagnostic” fee (on top of my service contract). The second tech did some of the same things, tightened up some connections, and skipped off without charging anything (3 days after the first tech), but advised me that the thermostat would need to be changed because it doesn’t go with the furnace I have (the thermostat came with the house when I bought it 10 years ago, so maybe that’s true…?). The third tech gave me the bad circuit board/replacement news (2nd and 3rd tech, same tech). He said that he left the house with “some heat, but not much” and that he would get some numbers for me from his home office and contact me tomorrow for financing options.
    I’m not sure I can trust the 2nd/3rd tech… would it be possible that the thermostat does need to be replaced, since my dual stage furnace seems to be igniting and staying on for a good while? I’m not sure when it ‘craps out’, but the house goes from being warm to fairly freaking cold in an overnight situation when it is 20 degrees out… i’m in the Atlanta area. Love to have your advice on this before I commit to a furnace replacement. Thanks!

    1. Hi Karen! Sorry that you are having trouble with your furnace. The only reason why I would recommend replacing a furnace would be if the heat exchanger is cracked of if the furnace presents a dangerous condition to the home owner. I would suggest replacing the flame sensor. Sometimes just cleaning the flame sensor does not fix the problem. Most of the time when furnaces have trouble lighting is when they are cooled down and cold. So maybe during the middle of the night the furnace or flame sensor cools down and does not sense the flame then this sends the furnace into lock out mode until the switch on the side is reset. The next time the furnace goes out please reset the on/off switch on the side of the furnace and watch to see if the furnace lights or not. It would not hurt to replace the thermostat. Most of the time when a furnace messes up there will be a blinking code on the control board that tells what problem the furnace is having. Most of the time what the blink code means is located inside the furnace blower door on a label or somewhere on the furnace. The next time your furnace messes up I would suggest trying to read the blink code on the control board. Most of the time furnace manufacturers will place a viewing window in the furnace blower door so you can see the blinks. It sounds like you have a real nice two stage furnace. Most of these high efficiency furnaces have at least a 20 year heat exchanger warranty and most have a life time warranty. I would hate for you to waste your money on a new furnace when you really do not need one. If you would like for me to look up parts please send your furnace’s model number. If it is a Bryant or Carrier I will need the product number. Best of luck! Steve

      1. Steve,
        Thanks so much for your prompt response, and for helping those of us who are not literate in the world of heating and cooling! The process of just reviewing your Q&A sessions makes me feel much smarter about HVAC – a great help to all who come here, I am sure. I am scheduled to be home this weekend, so I will take a look at the furnace and troubleshoot as you have suggested. My parents are living with me, so they are dealing with the weekday cold front, but hopefully the electric heaters will get them through until I can arrive.

        Thanks again, and I will certainly come back to report what I have found. Have a great day!
        Karen

      2. Hi! If the code flashes are right then it sounds like the furnace is over-heating and going off on limit. This can be caused by a dirty air filter, dirty or stopped up AC evaporator coil, slow blower motor (might need a new capacitor), or a furnace that has too much gas input or pressure (might need to adjust gas valve). Below is a parts list for your furnace model. Here is what I found when I searched for the control board part number online: https://www.google.com/#q=PCBBF115S+amana+control+board Tech seems to think the circuit board is dropping the draft inducer out. So he thinks it is the circuit board sounds like to me. If he suggests the dual stage thermostat then I would probably go with the two stage even though most two stage furnaces will work on a one stage thermostat and allow the circuit board to determine after running in low stage heat to kick into high stage heat after 10 minutes. I hope the tech can get it fixed without anymore expense. Steve
        Total: 77 Parts Model#: GUIV115CX50 Mfg#: P1230207F
        Part Number Description Type Substitution
        A4002702 BLOWER MOTOR GROMMET
        A4554801 SNAP BUSHING OBSOLETE
        A4568804 GROMMET-D
        B1370818 INTERLOCK SWITCH 0130M00243
        B1392104 UNIVERSAL BUSHING UB 875
        B1410310 PRESSURE SWITCH HOSE B1410310Q
        C6121806 BLOWER CUT-OFF
        C6349703 TRANSFORMER F
        C9443701 MOTOR MOUNT BRACKET R9900181
        D6723303S BLOWER WHEEL F
        M0221461 TC SCREW
        M0267144 MACHINE SCREW OBSOLETE
        M0282015 KEPS NUT
        PCBBF115 IGNITION BOARD, HSI INTEGRATED F PCBBF115S
        RP6620033 REPAIR PARTS MANUAL S
        0151F00000P GAS VALVE – WHITE-RODGERS 2-STAGE F 0151F00000PS
        0231K00013A MOTOR 3/4 HP PROGRAMMED F
        10123525 RESET LIMIT, MANUAL (AUXILIARY) F
        10123531 MANUAL RESET LIMIT-LIGHT PURPLE F
        10568804 MANIFOLD OBSOLETE
        10690002 DOOR CATCH ASSY
        10690301 FILTER ANGLE OBSOLETE
        10716003 ORIFICE F 0163F00018
        10728336 PRIMARY LIMIT F
        10734413 BURNER BOX OBSOLETE
        10734504 BURNER BOX TOP OBSOLETE
        10734609 BURNER BOX FRONT
        10734704 BURNER BRACKET LOCK OBSOLETE
        10735003 IGNITOR F 10735003A
        10735102S BECKETT BURNER F
        10735201 FLAME SENSOR F
        10736102 HIGH VOLTAGE BOX 0161F00012S
        10736201 COVER, HIGH VOLTAGE BOX
        10744901 BLOWER SIDE RAIL OBSOLETE
        10744902 BLOWER SIDE RAIL OBSOLETE
        10746205 CONTROL BRACKET OBSOLETE
        10759617S USERS MANUAL F
        10759824S INSTALLATION INSTRUCTIONS S
        10764320 ROTATING PLATE
        10764406 PARTITION PLATE OBSOLETE
        10764601 ROTATING PLATE GASKET
        10772907S INSTALLATION INSTRUCTIONS S
        10861101 AUXILIARY LIMIT BRACKET
        11001301 COMPARTMENT GASKET OBSOLETE
        11008104 BURNER BRACKET [OBSOLETE] OBSOLETE
        11008703 SENSOR BRACKET [OBSOLETE] OBSOLETE
        11009701 TRANSITION PLATE TOP OBSOLETE
        11034809 BLOWER DECK
        11072204 ORIFICE SHIELD
        11072302 ID BLOWER TRANSITION OBSOLETE
        11094104 HEAT EXCHANGER ASSY 5B
        11094903 CORNER BRACKET
        11104001 VIEWPORT BUSHING-ACCESS DOOR OBSOLETE
        11118705 WIRING HARNESS 16-PIN F
        11142203 COLLECTOR BOX/ID GASKET
        11176907 WIRING HARNESS F OBSOLETE
        11177105 PRESSURE SWITCH F
        11177202 ID BLOWER
        11185804 BLOWER HOUSING ASSY 11185817
        20006603 INSULATION
        20024603S VENTING MANUAL F
        20158901 INTERFACE BOARD
        20159002 WIRING HARNESS F
        20159103 WIRING HARNESS F OBSOLETE
        20213106 NAMEPLATE S
        20213213 NAMEPLATE-AMANA S OBSOLETE
        20214001 BOARD PLATE
        20218901 COIL-INDUCTOR F 0130M00142
        20242801 FILTER RAIL
        20243502 SIDE INSULATION 20243503
        20272803 BLOWER DOOR
        20272903 ACCESS DOOR
        20273203 BACK PANEL OBSOLETE
        20273309 FLUE COVER
        20273405 BASEPAN
        20273601 SIDE PANEL LH [OBSOLETE] OBSOLETE
        20273701 SIDE PANEL RH OBSOLETE

      3. Hi Steve,
        I have gathered some more information, and a snapshot of the 3rd technician’s diagnosis and recommendation from yesterday’s invoice:
        ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
        Brand Model Serial #
        AMANA GUIV115CX50 9906220939
        Circuit board is dropping out induce draft motor when igniter comes
        on. Will price the component. Unit has single stage Tstat that needs
        to be a two stage thermostat
        Cost of these components will be emailed. Please reply to email to
        get parts ordered
        ~~~~~~~~~~~~~~~~~~~~~~~~~

        I have read that a two-stage thermostat is not a necessity, but if I need to replace the thermostat anyway, should I opt for the two-stage model? Also, my father seems to remember the tech counting 4 flashing lights on the circuit board, and from what I can gather in the operating manual, that could be one of four things:
        1. a faulty limit or rollout switch
        2. an open auxiliary limit
        3. improper air flow or distribution
        4. cycling on limit

        After further reading the manual, it looks like a remedy for this situation (since I do get heat, just not sufficiently or consistently) might be to replace the induced draft blower, which looks like what the tech is sort of referencing. Could he be leading me in the right direction with a replacement of the circuit board, in that case?

        Thanks in advance for your advice, again!
        Karen

    2. Just wanted to thank you for your help. Our furnace was not putting out hot air. I read your advice as to what it might be to my husband. He than watched your video about cleaning the flame sensor. He tried it and now we have a warm house again. THANK YOU THANK YOU THANK YOU.

      1. Hi Karen! Thank you so very much for taking your time to write us back with the great news! Congratulations on repairing your furnace! I am glad to hear that it was an easy fix and we were able to help you out! I hope you and your family have a blessed and happy 2016! Steve

    3. Hello, my heater brand is York, and is like 15 years old .
      When I turn on the heater, the ignite turns red for a few seconds and then turn off.
      I dont see any fire on at all.
      Thank you!
      Alma Garza

      1. Hi! This could be anything from a control board problem to a gas valve problem. Normally the ignitor will glow for 20 to 30 seconds so this makes me feel that it might be a relay on the control board that sends power to the ignitor. I would suggest that you go through our furnace trouble shooting flow chart to determine where the problem is. Here is a link to our furnace troubleshooting flow chart page: https://arnoldserv.wpengine.com/furnace-trouble-shooting-flow-chart/ Please send me your furnace’s model number if you would like for me to look up parts. I hope you can easily find and fix the problem. Steve

  36. I have a carrier heater on natural gas. It is the original heater in the house from 1977. My pilot light stays lit, lights the burners the blower motor will kick on and blow hot air. It will run for about 10 minutes and all flame goes out even the pilot.

    1. Hi Jeff! Sorry to hear your furnace is not working right. What we would need to find out is… what control or what problem is causing the furnace to cut off prematurely. I would suggest that you test with a volt meter set to “Volts AC” the W and C wires on your furnace’s control board to make sure the thermostat is supplying a constant 24 to 24 volts AC to the control board when the furnace burner and pilot goes off. If the thermostat is cutting the furnace off then you might have a thermostat or heat anticipator problem. We have a basic furnace troubleshooting page with a furnace troubleshooting flow chart on the following page: https://arnoldserv.wpengine.com/gas-electric-furnace-troubleshooting-simplified-2/ This could be something as simple as a thermostat problem. This could also be a limit or rollout switch which is causing the furnace to go out. I know a lot of the old Carrier furnaces have the 3 wire pilot burner that if the pilot is not good and blue of if the pilot is dirty it will cut everything off. You might want to clean the 3-wire pilot burner. We sell the 3 wire pilots on the following page: https://arnoldserv.wpengine.com/product/bryant-carrier-3-wire-pilot-burner-lh680005/ I hope you can easily find and fix the problem. Steve

      1. The pilot flame is bright and blue. The thermostat will kick on and eventually activate the blower motor. The main flames will run about 6 minutes and turn off leaving the pilot light lit with the blower blowing. It will cycle the main burners again and run for about 6 minutes again and this time when it goes out it’ll take the pilot light with it. My thermostat is battery operated by two AAs. Should I change those?

      2. Yes, I would check the batteries. Really about the only way to be sure what is causing the problem is to test the controls with a volt meter when the burners kick out. This will tell you if it is the thermostat or another control causing the problem. Best of luck in finding the problem. Hope you have a blessed day and a Happy New Year! Steve

  37. I have a goodman 2 burner furnace that the main burner will light but the secondary only lights if I run a wire through the jet. I’ve taken the jets off and cleaned them, they are wide open, I’ve blown compressed air through the tube that holds the jets, the burner when both light are burning nice and the crossovers seem clean, the problem is only with the second burner.

    1. Hi Jim! Since you have cleaned the burner orifice and blown the tube out that goes to the orifice jets…the next thing that I would try would be adjust the gas pressure up a little bit on the gas valve. You might not be getting enough gas to light the second burner. If you do not feel comfortable in doing this then I would recommend calling in a professional. I suggest to not turn the gas valve regulator screen more than 1/4 turn at a time. There is a good YouTube video on the following page that discusses this: https://www.youtube.com/watch?v=VXXVHAbZUCU I explain how to do this in number 6 on the following page: https://arnoldserv.wpengine.com/gas-electric-furnace-troubleshooting-simplified-2/ I hope that adjusting the gas pressure fixes your problem. Steve

  38. My furnace main burner ignites, the main burner stays on for 3 to 5 seconds, then shuts right back off. It tries this ignition sequence again, and the same thing happens. After 3 times the furnace goes into lock out. I replaced the flame sensor, but it has the same problem. I called a bad technician who told me that the ignition part needed to be replaced, which I doubt because the flames start. Could this be the problem? Like I said, the flames fires up for a few seconds, so I consider that this part is OK. The technician also told me that the electronic board was bad, and that need it to be replaced.

    Rheem Criterion II Model Number RGPH-12NARJR

    1. Hi Omar! If the furnace continues to have a flame proving problem then I would suggest that you check all wire connections to make sure they are good, tight and not burnt. Please make sure the ground on the furnace is good and tight. Please make sure the flame sensor is sitting in a good blue flame. Yes, If this does not fix the problem then you might need a new control board. Please send me your model number and serial number if you would like for me to look up the part number for the control board. I will need the first two letters of the serial number. Thanks! Steve

      1. Steve,
        I check the voltage across the flame sensor (chassis and the end of the flame sensor). I got 106V with the door switch off, as soon as I press the switch to turn the circuit board, the voltage across the flame sensor drops to .4 V, as soon as I turn on the thermostat, the voltage moves up to 0.6, when the igniter turns on, voltage moves up again to 1.01V, when the flames fires voltages moves up again to 1.4. When the igniter turns off and the gas valve shuts off, the voltages drops again to .4v. Could the circuit board be bad? Why the voltage across the flame sensor drops to 0.4v as soon as I turn on the circuit board?
        Rheem Criterion II Model Number RGPH-12NARJR
        Control board: rheems 62-24084-02

      2. Hi Omar!
        This sounds like you have a short in your wiring somewhere. You should not be getting any voltage across the flame sensor. This could be a short in the control board. The 62-24084-02 control board that you have has been updated to control board 62-24084-82. I do not understand why you are getting voltage to the flame sensor with the door switch off. Sounds like a shorted wire or shorted control problem somewhere. You might want to get a professional to troubleshoot this. Sorry that I can not be much help. Steve

  39. We have replaced the ignitor 3 times within 2mos. Any ideas why it keeps going bad? The first time it was an after market part and thought it just might not be a very good brand. 2nd time we got a better brand so we thought, lasted about a week. 3rd time we have bought a sodium nitride ignitor which we thought would be more durable well after one week it has stopped sparking again and thus, no heat again. We have a Goodman furnace model #GPD075-3. Thank you

    1. We have an article listed on the following page that describes why an ignitor might go out prematurely under the section: “Below are listed some reasons that might cause your ignitor to go out prematurely” Here is a link to our page where we discuss this problem: https://arnoldserv.wpengine.com/gas-electric-furnace-troubleshooting-simplified-2/ Our Goodman parts program shows that your furnace uses the B1401018s ignitor. You might consider purchasing the 0230K00001 ignitor kit that we sell on the following page: https://arnoldserv.wpengine.com/product/goodman-furnace-hot-surface-ignitor-conversion-kit-0230k00001/ This kit is a more durable ignitor. You might want to make sure that your ignitor is not staying on after the gas on the furnace is ignited. If the ignitor is staying on more than 15 seconds after the gas ignites then this could cause the ignitor to burn out prematurely. The ignitor timing is controlled by the furnace control board so you might need a new control board. Our parts program shows that your furnace uses the B1809913S control board that we sell on the following page: https://arnoldserv.wpengine.com/product/goodman-furnace-control-board-b1809913s/ Please make sure all wire connections, plug connections and ground on your furnace are good and tight. A loose connection can cause high amp draw and burn out electrical parts. Best of luck in finding the problem. Steve

  40. Steve,

    Question I have a carrier furnace number 58pav111-13112

    I have noticed that when it starts up the flames sometimes does not evenly start across the orifices. could it be a dirty flame sensor?

    1. Hi Robert! This sounds like your furnace burners might be dirty or you are not getting enough gas pressure to the burners. I would suggest turning the furnace off then taking the burners out and blow them out with compressed air or use a vac on them. We show how to adjust gas pressure on the following page: https://arnoldserv.wpengine.com/gas-electric-furnace-troubleshooting-simplified-2/ About half way down the page. If you do not feel comfortable in doing this I would suggest calling in a professional. The burners should light completely across all burners so the flame sensor can pick up the flame. Your furnace uses the LH680014 flame sensor that we sell on the following page: https://arnoldserv.wpengine.com/product/bryant-carrier-furnace-flame-sensor-lh680014/ If the burners are lighting all the way across the flame sensor is not the problem. Please see the following screen shot picture that shows critical parts for your furnace: http://screencast.com/t/nmxBxJssfOnZ Best of luck in finding the problem. Merry Christmas! Steve A.

  41. My furnace started having problems out of no where (10 year old unit).

    Furnace flu fan kicks on ignitor glow for a sec at times then shut down. Sometimes it would ignite the pre flame for a couple seconds then shut down. Sometimes it would light completely, all three shoots, then shut down Completely. Led light on gas valve always blinked like nothing wrong.

    Replaced flame sensor and hot ignitor and started up fine…. For a little bit. Shut down early then fire up and work for a bit. Now it is back to the beginning problem. All these times it never tripped any of the reset sensors and one one time did the led flash for multiple start up failure.

    Is it time for a new board? Honeywell

    1. Hi Brian! Your problem sounds like a relay on the control board that provides power to the ignitor is failing. Sometimes when the little relay contacts on the control board become pitted and worn out the furnace will act the way you describe. Sometimes the ignitor will light and glow and other times it will not. Please make sure that your pressure switch is staying closed all the time during the ignition sequence and please check all the wires and connections on the furnace to make sure they are good and tight and not burnt. Sometimes a pressure switch will open and close during ignition especially on a windy day or a loose wire connection will cause the problem you are having. This sounds like a control board issue to me. If you would like for me to look up parts please send me your furnace’s model number. If you have a Bryant Carrier furnace I will need the product number. I hope you can easily find the problem. Steve

  42. I have a Trane / American Standard model #ycc042F1MOBA. I’m having trouble with my furnace lighting and then kicking off after a few seconds. I cleaned my flame sensor and it got better than it started acting up again. One thing I’ve noticed is when the unit shuts down my purge fan stays running. I’m having trouble finding a flame sensor using this model number. The closest sensor number I could find was Sen0233. Any ideas would be appreciated.
    Thank you
    P.S. These are the numbers that were on my sensor “929643P01”, “PSE TR4”, “9233”

    1. Hi! Our Trane parts program shows that your furnace uses flame sensor part number SEN00297 which we sell on the following page: https://arnoldserv.wpengine.com/product/american-standard-trane-furnace-flame-sensor-sen00297/ Please see the following screen shot picture that I took from our Trane parts program: http://screencast.com/t/uQWTw5DYBkTo Please make sure all your wire connections and ground connections are good and tight. We have the flame sensor in stock. I hope this solves your problem. Steve

  43. Burners light for a few seconds then go out. I cleaned the flame sensor and it worked only a couple times, and problem returned. I replaced the sensor with a new one, it worked then problem has now returned again. Could it be another issue?

    1. Hi Anthony! Please make sure that the ground is good on your furnace and all connections are good and tight. A burner flame that is not good and blue and not touching the flame sensor can cause the flame sensor to not sense a good flame. Please make sure the flame sensor is sitting in a good hot blue flame when the burners come on. Sometimes the problem can be in the control board. Best of luck in finding the problem.

  44. Thanks, this tip on cleaning the flame sensor kept my thanksgiving warm!

    1. Awesome! Glad to hear you fixed your furnace by cleaning the flame sensor! Thanks so much for letting me know our page helped you out! Hope you and your family have a blessed Thanksgiving and Christmas Holiday! Steve

  45. My burners work fine while the cover is off but they go out soon after I put it back on. I can feel it pulling air through when it is cracked. When the cover is on it will burn out then ignite Every minute or so. What could be wrong.

    1. Hi Jesse! This sounds like an air fuel mixture problem. Please check to make sure that your pressure switch is staying closed when the gas burners go off. If you have an obstruction in the vent or a leaking heat exchanger the furnace will act like you are describing. You can test a pressure switch the same way that I show how to test a rollout switch on the following page: https://arnoldserv.wpengine.com/gas-electric-furnace-troubleshooting-simplified-2/ The rollout switch testing is a little more than half way down the page. I Googled pressure switch testing and came up with the following: https://www.google.com/#q=testing+a+furnace+pressure+switch I hope you can easily find the problem. Steve Arnold

    2. I’ve had this very same issue with a Bryant high efficiency unit. It turns out the air intake pipe from the roof was blocked and the unit could draw clean/cold air into the combustion chamber. Remove a wasp’s nest and all was good.

      1. Thanks so much for telling us about the wasp’s nest in the vent pipes blocking the furnace vent. I hope you have a great day! Steve

  46. I have a comfort maker main burner kicks on for about 15 seconds (3 times) then the second one kicks on for about 30 seconds and the both go out. I have replaced the flame sensor, gas valve ( smart valve) ,pressure switch . I don’t know what else to try.

    1. Hi Mr. Ralston! Since that you say one burner kicks on for about 15 seconds and the second burner kicks on for about 30 seconds this tends to make me believe that you do not have enough or you have too much gas pressure coming out of your gas valve. Normally, both burners should light at the same time and burn continuous until the wall thermostat is satisfied. Your furnace gas is probably cutting off because the flame sensor is not sensing the flame on the burners so it tells the control board to cut the furnace off. Adjusting gas pressure can be dangerous. I would suggest leaving this to a professional who has a Water Column gage. Here are some links to some YouTube videos if you feel comfortable in trying yourself: https://www.google.com/#q=youtube+adjusting+gas+pressure+furnace Best of luck in fixing this problem. I hope you have a great day! Steve Arnold

  47. I got a 2yr old Goodman…its goes through the cycle properly….after the blower comes on for maybe 30-40 seconds…the burners goes out…..I change the pressure switch…flame sensor and control board…..and its still cutting out early….I check the flute pipe…and voltage…….still cuts out…..I’m all out of ideas as to what is happening..

    1. Hi Dante! About the only way to find out for sure where the problem is would be to use a volt meter. If you do not have a volt meter it will be a guess as to where the problem is located. I would suggest that you purchase a low cost multi-meter at Home Depot, Radio Shack or other electronics store. When you get the meter I would suggest sitting it on “Volts AC”. Tape the furnace blower door safety switch down so you can get power to the furnace with the blower door open. Turn the thermostat up for heat and test between the thermostat wires W (white) and C Com (usually purple or blue on Goodman). You should get a constant 24 to 28 volts AC between the W and C terminals when the thermostat is calling for heat. If the voltage cuts out when the furnace goes off then you probably have a thermostat problem. Please make sure the batteries are good on your thermostat if your thermostat has batteries. Next, I would check all the safety controls, the pressure switch, limits and rollouts to make sure they are all closed when the furnace flame goes out. I know that on Goodman there is a somewhat hidden limit control that sits on the bottom of the blower housing. Please make sure this limit is checked out and not missed. I have missed seeing it before. If all of these safety controls are closed when the furnace gas goes off then I would check the gas valve. If you are getting 24 volts to the gas valve and it is not opening then this could be a gas valve problem. We have a furnace troubleshooting flow chart on the following page: https://arnoldserv.wpengine.com/wp-content/uploads/2014/12/furnace-troubleshooting-flow-chart.pdf I hope this will help you find the problem. God Bless you and your family. Steve Arnold

  48. mine does this and has no sensor. its just a spiral ignitor with a hot surface ignitor box. Changed the spiral ignitor and still same problem. Do I change the gas valve or the HSI??

    1. Hi Joe!
      It is very unusual for a furnace to not have a flame sensing device. Please send my your furnace’s model number and I will try to look up the parts for your furnace. You would need to determine what device is causing the gas to cut off prematurely. I have seen safety devices (pressure switches, limits) cut off the gas burner’s prematurely. You would need to test with a volt meter to make sure all your safety devices are staying closed when the furnace cuts off including the thermostat connections between W and C on the control board. You should get a constant 24 to 28 volts between W and C on your control board. The hot surface ignitor should not be the problem. The purpose of the hot surface ignitor should only be to ignite the natural gas at the furnace burners. Since the gas is staying on for a short time I would think that the Gas valve is not the problem. Best of luck in finding and fixing your problem.
      Steve

      1. Steve – Similar to Joe N, our furnace also does not have a flame sensor. I’ve looked at every spot and cannot locate anything that resembles one. I’ve followed all wires and there aren’t any that lead into a location where a sensor might be hiding.

        I’ve tried checking the web for information on our furnace, but cannot seem to find much info. The furnace we have is… Rheem RGDG-07NAUER.

        I’ve read that not all furnaces have flame sensors. If that is the case, and mine doesn’t, what would be causing the furnace to power off before getting to the temperature set on the thermostat?

        Thanks in advance.

        Mike T

      2. Hi Mike! Please send me the first two letters of your serial number and I will be able to tell you if your furnace has a flame sensor or not. I hope you have a great day!
        Steve

      3. Steve

        Serial Number begins with CD

        MIke

      4. Hi Mike! Our Rheem, Ruud parts program shows that your furnace uses flame sensor part number 62-23543-01 that we sell on the following page: https://arnoldserv.wpengine.com/product/rheem-ruud-furnace-flame-sensor-62-23543-01/ If your furnace is cutting off before it reaches temperature on the thermostat I would suggest that you check your limit on the furnace to make sure it is staying closed all the time. If the limit opens it will cut the gas off until the furnace cools down. Also test between terminals W and C (com) and make sure your thermostat is not cutting the furnace off early. Please make sure if your furnace has batteries that the batteries are in good shape. Best of luck in finding the problem. Steve

      5. Steve

        Thank you for your time and assistance.

        I’ve checked the links you provided, and read through 92-23651-01-01 Installation Instructions. I’ve gone through the furnace again, but cannot locate the flame sensor.

        Here is a picture of my furnace… http://i.imgur.com/ACJPxyQ.jpg

        Are you able to see it?

      6. I should have caught this earlier, Sorry. Our program shows that your furnace uses the 62-24084-82 control board and if your furnace was built before the 32nd week of 1994 it might not have a flame sensor and the only way to add a flame sensor that I know of is to upgrade to the new board and purchase the flame sensor kit 62-24044-71. You should be able to tell if your furnace was built before F3294 by the serial number on your furnace. I should have asked for the full serial number. Please see the following screen shot from our parts program: http://screencast.com/t/pdJugNALxEJr We sell the control board on the following page: https://arnoldserv.wpengine.com/product/ruud-rheem-furnace-control-board-62-24084-82/ We sell the flame sensor kit on the following page: https://arnoldserv.wpengine.com/product/ruud-rheem-furnace-remote-flame-sensor-kit-62-24044-71/ If the burners on your furnace are staying on longer than 15 seconds then more than likely the flame sensor is not the problem. If you have a flame sensor problem the furnace burners only stay on from 1 to 10 seconds. Best of luck in finding the problem. Steve

      7. No worries Steve. I truly appreciate the help.

        My full serial number is CD5D302 F4792 0623

        I’m wondering if this unit does not have a flame sensor, perhaps the Rollout Limit Switch is going bad, which I see is #47-22861-01 on your site.

        I’ll keep an eye on this since it doesn’t happen each and every time I run the heater.

        Thanks again for your help. I hope you have a wonderful holiday.

        MIke

      8. Hi Mike! Yes, according to your serial number your furnace was made the 47th week of 1992 so yes, you would need to purchase the new board and the flame sensor kit to add a flame sensor to your furnace. When the furnace acts up you should be able to test the rollout switch and the limit switch with a volt meter to see if the circuit is opening on the rollout or limit. A pressure switch that opens up can also cause the gas to cut off. I show how to test rollouts with a meter on the following troubleshooting page we have: https://arnoldserv.wpengine.com/gas-electric-furnace-troubleshooting-simplified-2/ I hope you have a blessed day and weekend! Steve

  49. thanks for the info and the video it gave me the confidence to have a second look at the problem . sure enough it was the sensor and it was not much debris on it , a cleanup and it was fine
    thanks
    again

    1. Great! Awesome glad to hear that you were able to fix your furnace problem. Thank you so very much for taking your time to tell us the great news! Hope you have a blessed day! Steve

  50. This is our first blog posts. I will be happy to try and answer any questions you have. Thanks so much for your interest and support in our website! Hope you have a blessed day! Steve

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