Posted on 46 Comments

Problem: My furnace’s ignitor does not glow? This could be a pressure switch, limit, roll out switch, or furnace control board problem.

I see this problem many times during the heating season here in Louisville, KY. When your thermostat calls for heat the draft inducer (please see pictures below) should start which creates a draft in your vent pipe. If your vent piping is open and your pressure switch is working properly the pressure switch will close the connection between two wires and send a signal to the control board saying, “Yes it is OK to continue with the ignition process.”

draft inducer full

 

Goodmandraftinducerwithtext

Above are pictures of a draft inducers showing where the pressure switch tube attaches. Pressure switch tubes sometimes attach on the top bottom or near the center of the draft inducer. These are just two of hundreds of different draft inducer designs. Some are metal and some are plastic. Most of the time draft inducers are plastic on 92% furnaces & metal on 80% furnaces. Make sure the opening where the pressure switch tube is attached to the draft inducer is open. Sometimes a small wire can be used to reestablish the hole. Make sure your water drain on a 92% furnace is open. If too much water backs up into the draft inducer it will not allow the pressure switch to close.

Also, all of your limit controls and other safety devices must be closed (a closed circuit between the two connections) to allow the furnace ignitor to glow and start the ignition process. If there is a break down in the pressure switch or other limit safety controls the furnace, for your safety, will not proceed with the ignition sequence. The computer chip inside the board says, Wooooh, something is wrong here! Most furnaces will try this sequence for a total of three times then lock out. On most furnaces the only way to get them out of lock out mode is to turn the switch (looks like a light switch) on the side of the furnace to off and then back on again.

limits three
Above is a picture of three different types of limit controls. The two on the ends should reset automatically when the furnace cools down. The rollout limit switch in the center has to be manually reset by pressing the button in on the top. All limit controls are there for your safety. Never by-pass these.

 

How do you test a pressure switch and other limit controls?

This is for people who are experienced with electrical equipment and the use of a Volt Ohm meter. *Please never by pass a pressure switch or limit control. The pressure switch and limit switches are there for your safety. In the top picture I am testing a rollout limit switch to see if it is good. You would test by setting your volt meter to “Volts AC” and test the rollout switch by placing one meter probe on one terminal of the rollout switch and your other meter probe to a good ground. Below I have the red probe touching the top terminal of the rollout switch and the black probe touching a ground (body) of the furnace. You can see the I am getting 25.85 volts which means the rollout is good on the top terminal. I would next test the bottom terminal of the rollout by touching the red meter probe to the bottom terminal on the rollout switch and the black terminal to ground. If I get 25.85 volts on the bottom terminal the rollout is good. If I do not get any voltage on the bottom terminal then the rollout has tripped and can be reset (if equipped) by pressing in on the little button or replaced. If your rollout switch is tripped you probably have a stopped up heat exchanger or a leaking heat exchanger. I would recommend calling in a service technician to find out why the rollout switch tripped. If you have an open limit control either the furnace has over heated or the limit has gone bad. Problems that would make a limit open up would be dirty filters, dirty evaporator coil causing a restriction in the air flow or a slow blower motor (check the capacitor on the blower motor to make sure it is good). A weak blower motor capacitor will cause the blower to run slow and eventually fail. Pressure switches, and limit switches can be tested with a meter in the same manner. With the furnace calling for heat you can test each of the terminals on the pressure switch to ground to make sure the pressure switch is closed. You should be getting between 24 to 28 volts from each terminal to ground if the pressure switch is closed. If the pressure switch is open you either have a stopped up vent, drain line (if you have a condensing furnace) or bad pressure switch. Below we have three pictures of pressure switches. The picture on the left shows the full view of one pressure switch. Please keep in mind there are many different types. The picture on the right shows the two terminals that you can use to test to see if the pressure switch is operating properly. The front terminal is burnt and discolored. This is a clue that this pressure switch has a problem. The picture on the bottom is a black Goodman, Janitrol plastic pressure switch.

 

testingrolloutgood
Above pic shows me testing a rollout switch.
pressure switch terminals
Above are two pictures of pressure switches. The pressure switch on the left came off a 92%
furnace. It has two connections for pressure tubing. One tube would go to the water collection
box and the other tube would go to the draft inducer. The switch on the right has a burnt front terminal.
Pressure Switch Goodman black
Above is a picture of a Janitrol Goodman pressure switch.

 

How do I test to see if a pressure switch is operating properly?

Set your meter to volts AC, turn your furnace on so it is calling for heat. The draft inducer should start. There should be either two or three wires going into your pressure switch. Probe one lead of the pressure with one lead of your meter while touching the other lead of your meter to ground. Ground would be any bare metal part of your furnace. This must be bare metal. I always try to touch the other lead of my meter to the furnace’s switch box. If you have a two wire pressure switch you should be getting 24 or more volts between both leads to ground. By this I mean if you touch one terminal of the pressure switch with one lead of your meter, and touch the other lead of your meter to a ground, bare metal part of your furnace, you should get 24 or more volts (24 to 28 volts). If you do not get 24 or more volts with the furnace running then you have a pressure switch problem. Your vent could be stopped up, The tube that runs from your pressure switch to the draft inducer could be plugged up or the draft inducer hole could be plugged up. On high efficiency condensing furnaces the water drain line could be stopped up, causing a water back up and blockage in the pressure switch tube. I usually take the drain hose loose from the condensing furnace and use a wet vacuum to open the drain back up. I hope this will help you in troubleshooting your gas furnace pressure switch. If the pressure switch, limit and rollout switches are all closed when the furnace is calling for heat then this could be a bad ignitor. We sell many different types of ignitors for many different brand furnaces on the following page: Please click here to see the furnace hot surface ignitors we sell. Please send us your furnace’s model number if you would like for us to find the right parts for your furnace. Our email address is:  arnoldservice@gmail.com

 

 


46 thoughts on “Problem: My furnace’s ignitor does not glow? This could be a pressure switch, limit, roll out switch, or furnace control board problem.

  1. 1996 carrier bryant furnace , I keep getting error code 34 there is no power going to the igniter it’s not lighting, it goes thru the sequence but the igniter does not light.

    1. Hi Laura!
      If there is no power going to the ignitor then you could have an open safety control like a pressure switch, rollout switch, or a limit switch. I would suggest that you test with a voltmeter and make sure all the safety controls are closed and allowing electrical current to flow through them. If a safety control is open then it will not allow the ignitor to glow. You could also have a control board problem. The ignitor relay on your control board might be bad. I would rule out the safety controls being open first. I would suggest making sure that you test the ignitor with an ohmmeter to make sure that the ignitor is good. You should get between 40 to 90 ohms if the ignitor is good. If you would like for me to look up part numbers for you please send your furnace’s product number to our email address arnoldservice@gmail.com. I hope you can easily find and fix the problem. Steve

  2. Hey I am having a problem with my luxaire furnace at first the burners were not staying lit and would go out every few minutes. So I replaced all the switches and now my igniter wont glow, I have checked all the connections to double check that they are a tight. And last monthe we replaced the igniter so it should not be bad either, and it worked fine before I put in all the new switches

    1. Hi Holly! I really do not know what you mean when you say that you replaced the switches. Are you referring to rollout switches, limit switch, or furnace door safety switch? You should do a test with a voltmeter to test the switches to make sure they are working. We have another post that might help troubleshoot your problem on the following page: https://arnoldservice.com/problem-furnace-will-not-ignite-ignitor-will-not-glow/ We have a post about testing rollout switches on the following page: https://arnoldservice.com/problem-i-replaced-my-rollout-switch-and-the-furnace-still-goes-out-after-running-12-hour/ I would like to suggest that you do and ohm test on your ignitor to make sure that it is good and then do a test to see if the ignitor is getting 110 volts the make it glow by testing with a voltmeter. I hope this helps you out. Steve

  3. Hello Sir!

    I have Armstrong Air furnace model GUJ100D12-3A. It runs heat cycle when I short pressure switch terminals. During normal heat cycle (removing pressure switch short), igniter doesn’t glow, but just inducer motor keeps running. I cleaned rubber tube and both ends where rubber tube is connected. When I measure resistance when inducer motor is running, and both terminals still connected, it shows between 15 ohm to 40 ohm. Shouldn’t it show almost zero? I do not hear any noise in inducer or see any blockage. It runs freely.

    1. Hi David! I am sorry, but I do not have an Armstrong furnace parts program where I can look up parts. You might need a new pressure switch. We have posts about pressure switch troubleshooting, problems with YouTube videos on the following two pages: https://arnoldservice.com/how-to-test-and-troubleshoot-gas-furnace-pressure-switches/ and https://arnoldservice.com/problem-furnace-blink-code-shows-i-have-a-pressure-switch-problem-replaced-pressure-switch-still-have-a-problem/ I hope this helps you find out what the problem is with your furnace. Sorry, that I can not be of much help.

  4. Hi Steve,
    Both my inducer pressure switch and high limit switch are not getting voltage from either terminal when there is a call for heat to the furnace. I had been able to get the system running earlier by first cleaning the flame sensor and then pressing on the 12 pin connector to the board, but now nothing works. I have continuity through the high limit switch and pressure switch with the inducer running. I’m thinking messing around with the flame sensor was just a red herring and something is wrong with the board. My next step is to replace the control board. Any thoughts? I am getting four blinking red lights (York furnace) which indicates a high limit trip. Should the limit and pressure switches still get voltage when in a lockout mode? I’m going to try cutting power for a bit to see if it resets the lockout and restores voltage, but I kind of doubt that’ll be the problem. Thanks for any help.
    Bryan

    1. Hi Bryan! So sorry to hear that you are having furnace problems during this cold weather! It is cold here in Louisville, KY! I really do not know if you should be getting voltage to the pressure switch and limit in lockout mode. I do know that you should be getting voltage on both sides of the limit (24 volts from each terminal to a good ground on the furnace) when the furnace is out of lockout mode. You should be getting 24 volts on one side of the pressure switch when the draft inducer is not running and on both terminals of the pressure switch when the draft inducer is running. Yes, since you said that when you played with the 12 pin connector the furnace started working then I would think you either need a new control board or a new connector. You might try a little dielectric grease on the end of the plug and make sure the plug is good and tight. If you would like for me to look up parts then please send me your furnace’s model number to our email address: arnoldservice@gmail.com. I hope you can get it fixed soon! God Bless you! Steve

  5. Hi Steve, My goodman furnace gets to the ignitor just fine, no gas to the pilot tube, during the 3 cycles it blows the fuse. I tried to listen to the valve to see if its opening but I don’t hear anything or couldn’t because of the fan running(used a short wooden handle) would that be the valve or control board.?

    Thanks,

    Mike.

    1. Hi Mike! I really have no idea why the fuse blows on your control board after 3 tries. This could be like you are thinking either the gas valve shorting out, control board shorting out or a thermostat wire shorting out. Any low voltage control which includes the thermostat could short out and cause the fuse on the control board to blow. I would like to suggest that you make sure all connections both high and low voltage wires are good and tight. Loose connections can cause arcing, high amperage and blow fuses. Also, check to make sure that none of the thermostat wires are pinched between the metal of the furnace body. Take the wires off the gas valve, set your meter to “ohms” and make sure that you do not get any resistance between the terminals of the gas valve to the body of the gas valve. If you do get any resistance then I would think that the gas valve is shorting out. If everything checks out OK then I would guess that the problem is in the control board. If you would like me to look up parts then please send me your Goodman model number to our email address: arnoldservice@gmail.com. I hope you can find and fix the problem soon! Steve

      1. Hi Steve,
        I replaced the control board ( mine had “bubbles” on it, part was in stock local so I replaced it.) and it still blows the fuse, 1st try of the system, gas comes on for a split second and fuse blows. I ordered a gas valve from ya’ll, 15 mins before 1, 🙂 can ya’ll make sure it gets on the plane.

        Thanks, Mike

      2. Thank you so much for your business, Mike! Yes, your Next Day Air order is shipping out today and you should have it tomorrow. I hope that the gas valve is your problem. Most of the time when fuses blow it is the thermostat wires. Have you tried taking all the thermostat wires loose from the control board and jumping the R to W wire. If the short is in the thermostat wires the furnace will work with the wires disconnected. I hope you have a great day! Steve

      3. Hi Steve,
        Ty for the fast service, valve did the trick.

        Thanks again,

        Mike

      4. Hi Mike! Fantastic! Great! Awesome! So glad to hear that you were able to fix your furnace’s problem by replacing the gas valve! Thank you so very much for your business and kind words! We are very blessed to have you as a customer! God Bless You! Steve

  6. Hi. My furnace was short cycling so I replaced the ignition sensor. Now the ignitor does not light. I replaced that just incase it went bad and it still will not light. I have shut all power off and tried booting it back up with no success, any suggestions would be appreciated.
    Thanks

    1. Hi Bernadette! I would suggest checking the safety controls like in the post above. Make sure that if you have a fuse on the control board that the fuse is good. Make sure if you have batteries in your thermostat that the batteries are good. The safety controls would be the limit, rollouts and pressure switch to make sure they are all closed and allowing current to flow through these controls. Some of the rollouts switches can be hidden. Make sure that your check any hidden rollouts to make sure the reset buttons are pushed in. I have found some rollouts hidden on the top or bottom of the blower housing on some furnaces. If all the controls check out OK then I would suggest checking to see if you are getting 110 volts to the ignitor when the ignitor is supposed to be glowing (probably about 30 seconds into the heating cycle). If you are not getting 110 volts to the ignitor then you probably have a control board problem. If you would like for me to look up the control board part number then please send me your furnaces brand name and model number. The model number should be located inside the furnace near the burner area. It would be best to contact us at our email arnoldservice@gmail.com. I hope you can easily find and fix the problem. Steve

  7. My hot surface ignighter on my payne pg9maa series F is getting constant power even after ignition. What could be causing this. I can unplug my ignighter after furnace lights and the cycle will run fine. Then for next cycle i have to replug and repeat? Thank you

    1. Hi Mike!
      More than likely the ignitor relay on the control board is stuck closed. You might want to try and tap on it (one of the little black boxes) with your finger to see if the relay will release (break contact). If you want me to look up the control boar that you have please send me your furnace’s model number. If you have a Bryant or Carrier furnace I will need the product number. I hope you have a Merry Christmas! Steve

  8. Hi, My igniter only gets votage for a few seconds and does not glow, new on does the same thing I did replace the module about10 or more yrs ago. I have checked everything including rollout and pressure swith and all is good. module tkype I replaced was white rodgers 50E47-843. Lights up yellow self check then green on furnace cycles and 120v goes to igniter for 1 or 2 sec and then nothing. I don’t hear or smell any gas and gas valve is getting 24 to 28 volts. tested igniter with 120 volts and it lites up.

    1. Hi Kerry! It sounds like you need another new control board since the voltage is dropping out going to your ignitor. This is a sign that the ignitor relay inside the control board is failing. I hope that a new control board fixes your problem. Steve

  9. Hi Steve,

    I have a tube heater installed in my garage, I’m not 100% sure if your article is relevant to a tube heater, but it does have all the components you are referring to.

    Here are the components:
    – Honeywell S89H hot surface ignition module (https://customer.honeywell.com/resources/Techlit/TechLitDocuments/68-0000s/68-0070.pdf)
    – It has a blower attached
    – Pressure switch
    – Gas Valve – Honeywell VR8205 (VR8205A2008)
    – Honeywell AT20B1064

    The problem:
    – this has not been turned on for about least 2 years (came with the house when I bough it last year)
    – when powered on, the blower runs, the glowbar glows, I can hear the value opening and closing, I think I also hear the pressure switch opening/closing, but it does not ignite
    – I’ve made sure all the gas cocks are in “ON” position leadign up to the gas valve (and it is also “ON” on the gas valve)

    1. Hi Kiri! I would like to suggest that you test the pressure switch with a voltmeter to make sure that the pressure switch is closing when the draft inducer is on and the thermostat is calling for heat. If the pressure switch is not closeing then you either have a pressure switch problem or a stopped up vent problem. Since you say that your ignitor is glowing and you can hear the valve opening and closing then I would think that the pressure switch and other safety controls (limit, rollouts) are closed and OK. I am just guessing about this problem, but if your furnace has not been on for over 2 years then you might have stale gas in your gas lines. The stale gas has to be bleed out before you get some good flammable natural gas. I have had my garage furnace do this to me before when I had not used it for a long time. I had to purge the gas line until I got all the stale gas out before my garage furnace would light. If you do not feel comfortable in doing this then you can keep cycling the furnace until some good gas comes through the gas valve. This might take 5 or 6 ignition tries depending on how long your gas line is before it gets good natural gas again. If you do not feel comfortable in purging the gas line then I would suggest you get an HVAC tech or someone who deals with gas lines. I hope this is the problem and you can get your garage heater going soon! I know we sure need it here in Louisville, KY. The wind chill is going to be in the single digits today! God bless you and your family. Steve

  10. Hi steve,
    I just replaced my ignitor but it is not glowing when the furnace kicks on. The furnace will just continuously blow cool air. Any thoughts?

    1. Hi David! I would make sure that all your safety controls are closed like the pressure switch, limit switch, and rollout switches. If the safety controls are all closed and allowing current to flow through them, then you might have a control board problem. I would like to suggest that you test at the plug where the ignitor plugs in and see if you are getting 110 volts out of the ignitor plug when the ignitor is supposed to be glowing. If you are getting 110 volts out of the ignitor plug then I would suggest testing the ignitor to see if the ignitor is good. The ignitor should read between 40 to 90 ohms if it is good. You might have a bad ignitor. I would also suggest reading the voltage where the ignitor plugs into the control board and see if you are getting 110 volts there when the ignitor is supposed to be glowing. If you are not getting 110 volts out of the control board then you might have a bad control board or ignitor relay on the control board. I hope you can easily find and fix the problem. Steve

  11. HELLO, MY FURNACE IS 2-3 YEARS OLD AND THE FALL WHEN WE START USING HEAT THE BLOWER (IF YOU WILL “FIRST PICTURE ABOVE” WILL FILL WITH WATER HAND TURNING IT YOU CAN HEAR AND FEEL WATER ABOUT 1/2 FULL ??? PLEASE ADVISE, DARRELL GREGG

    1. Hi Darrell!
      If you are referring to the blower housing being full of water then you could have a leaking air-conditioner coil pan, a dirty AC coil, a system that is low on refrigerant and causing the AC coil to freeze up, thaw out and produce water or a stopped-up condensate drain line. If you are referring to the draft inducer being full of water then this is most of the time caused by a condensate drain that is stopped up or if the furnace is not pitched properly. I would like to suggest that you disconnect the furnace pressure switch and blow the condensate drain line out with compressed air or use a wet vac to clean the drain line out. I did not receive your pictures. If you want to send pictures please send them to our email address: arnoldservice@gmail.com. I hope you can find and fix the problem soon! Steve

  12. Hi Steve, the ignitor on my furnace stay glowing during the entire cycle, and even after fire goes off the ignitor stays on along with the fan motor and the blower. I turned off the furnace at this point in fear of burning out the ignitor and blower. I think it may be the control board. What causes the ignitor to glow constantly like this?

    1. Hi Mike!
      Yes, I would surely think that you have a stuck ignitor relay on the control board that is causing the ignitor to not shut off. If you would like for me to look up which control board your furnace uses, then please send me the model number to our email: arnoldservice@gmail.com. I hope you have a great day and week! Steve

      1. Hi Steve, my heating unit will start n run for up too 3-4 hrs. Throw a code 4 High limit switch. Vents are good, vent pipe off inducer motor no blockage. Goes threw all cycles fine, but shuts off and has that code. Any suggestion on next step ?

      2. Hi Mr. Gainwell! More than likely you are not getting enough air flow through the furnace. Your blower motor could be cutting off in the middle of a cycle and letting the furnace over-heat. We discuss poor air flow in the following post: https://arnoldservice.com/problem-why-does-my-furnace-air-conditioner-have-poor-air-flow/ This could also be caused by having too much gas input/ btu input which would cause the furnace to go off on limit. You might need to adjust your gas valve to a lower BTU. setting so the furnace does not overheat. We have a post about adjusting furnace gas pressure on the following page: https://arnoldservice.com/adjust-gas-pressure-natural-gas-furnace/ i hope this helps you solve the problem. Steve

  13. My furnace stopped working, while troubleshooting I found that if I pulled the plastic tube from the pressure sensor to the combustion chamber the ignitor would glow and work but immediately shut off. I have checked for any blockage from the drain lines and also the plastic vent pvcs leading outside. The inducer was recently replaced. Could it be I have a bad pressure sensor or what? Not to mention, everything was working fine until this -40 weather hit! Anything to help me start before I call for HVAC to come look at it. Thanks Ken

    1. Hi Ken! You would need to check the pressure switch with a voltmeter to see if the pressure switch is staying closed the entire time the draft inducer is on. If the pressure switch is open then you might have a stopped up vent or a leak in the draft inducer. Yes, you might need a new pressure switch. I would suggest that you test the pressure switch and if it is closed then start looking for blockages in the vent, a stopped up furnace condensate drain or a loose draft inducer. Please make sure the draft inducer is screw tight against the housing of the furnace. If you have a 90% condensing furnace make sure that the condensate line is open and the water is not backing up inside the furnace. I would suggest taking the pressure switch tubing off and clean the condensate drain out with a wet vac. Make sure the drain line is draining properly. We have a pressure switch troubleshooting page that I hope will help you out: https://arnoldservice.com/how-to-test-and-troubleshoot-gas-furnace-pressure-switches/ Another suggestion would be to make sure all your safety controls are closed like the rollout switches, and limit switch. If you need a part please send me your furnace’s model number and I will be glad to make a recommendation. Our email is arnoldservice@gmail.com. I hope you can get the problem fixed soon! Steve

  14. Thank you Steve for the easy and educational read! After matching my furnace behavior to your explanation, it was only a few minutes to discover the fan housing opening to the pressure switch tube was encrusted. A few wire pokes later, a shot of compressed air and my heat was back. I will add that the depth of that passage into the fan housing was deceptively deeper than I anticipated and my first idea of a toothpick did not work, so wire and some air to ensure fluid communication. Thank you for saving us from the winter cold!

    1. Hi Kevin! Thanks so very much for sharing how you fixed your furnace! Congratulations! I am so glad to hear that you were able to get your furnace fixed on this cold winter night! God bless you and your family today and always! Steve

  15. Hi, and thank you, but I changed the igniter on my Bryant Furnace, but it still will not glow could my flame sensor prevent my igniter from glowing

    1. Hi Elliott! No, the flame sensor would not keep the ignitor from glowing. Some things that would keep the ignitor from glowing would be an open safety control like an open limit, open rollout or open pressure switch. I have also seen the ignitor relay on the furnace’s control board go out. If all the safety controls check out OK then you might need a new control board. I would suggest that you ohm out the new ignitor and make sure it measures between 40 to 90 ohms. I have seen some new ignitors be bad. I hope you can easily find and fix the problem. Steve

  16. Hi Steve, thanks to your post I’ve learned about the pressure switch tube and discovered that in my furnace it has slipped off its fan connector nozzle. Reconnecting the tube made the igniter to light up and the cycle to continue. Such a simple problem and an easy fix, and I was literally ready to start pulling my hair out. Before I discovered your site, I’ve already replaced what seemed a functional igniter (148 Ohms resistance) with a spare new one I had on hand, and have ordered a replacement control board on Amazon (attempting to cancel the order now).

    Thanks a lot for your informative post! I hope Google crawler picks up on it and more people can see it when searching for the furnace solutions.

    Dmitry.

    1. Hi Dmitry! So glad to hear that you were able to find an easy solution to your furnace problem! Awesome! Thanks so much for taking your time to share this with others! Yes, I hope Google and other search engines pick up our posts so it will help others. God bless you and your family today and always! Steve

  17. Is it possible to test the ignitor relay on the control board or does one replace the entire board? My ignitor will only glow on the 3rd or 4th ignition cycle, and over night when the thermostat is set back, we sometimes wake to a cold house. The thermostat is fine, all switches are operating normally. The ignitor is fine but only gets 120 volts on around the 3rd ignition attempt. The wiring from the control board to the ignitor is fine too. Could it be a cold or broken solder joint from 10 years of vibration? How does one check the relay or is there something else I should look for?

    1. This sounds like a bad ignitor relay on the control board just like you have concluded. The only way that I know to test it is by what you have already been doing and that is test the voltage going to the ignitor. Yes, sometimes the solder joints become loose from vibration or the contacts inside the relay become pitted and wear out. I am not electronically inclined where I could replace parts on the control board. I always replaced the entire control board. If you would like for me to look up parts then please send me your furnaces make and model number. Steve

  18. I have a Lennox gas furnace that is not heating. Igniter is new and although I have 118 ac at the connector it doesn’t glow?

    1. Hi Doug! Maybe you have a bad ignitor relay on the control board. I would suggest trying to test the voltage going to the ignitor when the ignitor (load) is plugged in. If the voltage is under 110 volts with the ignitor plugged in then you might have a bad relay on the control board or an open safety control like a roll-out, limit or pressure switch. I would suggest reading the ohms on the ignitor. A good ignitor will read from 40 to 90 ohms. I hope you can easily find and fix the problem. Steve

  19. And for those of us who have NO experience with furnaces, it might just need to be rebooted like a computer to start fresh; after all, there’s a circuit board inside! Both of mine were blowing air, but no heat, and this simple procedure won’t cause any harm. (1) open the cover; (2) if you don’t see a glow, the pilot light isn’t functioning and there will be no heat; (3) follow the power cord to the outlet, where there’s usually a light switch; (4) turn off the switch and wait for a few minutes before turning it back on; (4) this gives the furnace a chance to reset (reboot) itself and attempt to light the pilot itself. Worked for me, and no service call!! (If there isn’t a switch, don’t just unplug/replug the cord; you’ll want to turn it off at the breaker, wait for a few minutes, and turn on the breaker again.)

    1. Thanks you so very much for your advice! Great idea!

  20. My furnace operates perfectly if it has been off or is cool. After the first cycle, the ignitor does not appear to glow. If I allow it to sit for 20 minutes, then it fires right back up. Not sure why it ignites and burns sometimes but not others.

    1. Hi! Most of the time when the ignitor is erratic in operation it is caused by a control board relay that controls the ignitor contacts not making contact all the time and requires a new control board. If the furnace operates for a while, then shuts off and will not ignite again for 20 minutes, then I would suggest checking the limit and rollout switches to make sure all of them are staying closed. An open limit or thermostatic rollout will not allow the furnace ignitor to glow until the furnace cools down. We have troubleshooting page that shows how to test a rollout. The limit would be tested the same way. Here is a link to our troubleshooting page: https://arnoldservice.com/gas-electric-furnace-troubleshooting-simplified-2/ If you find an open limit or rollout then you probably have an air flow problem (dirty filter, stopped up evaporator coil, slow blower, etc.) or a stopped up heat exchanger or a leaking heat exchanger. I hope you can easily find and fix the problem. Steve

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