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Problem: Why does my furnace rollout switch have to be reset so often? Why do rollouts have different temperature differences?

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Problem: Why does my furnace rollout switch have to be reset so often? Why do rollouts have different temperature differences?

Answer:  The rollout switches and limits are determined by the engineers during the furnace building and testing process. Different areas of the furnace are allowed different heat measurements before they are determined to be safe or unsafe. If the furnace limit or rollout switch senses that over-heating occurs then it trips the rollout switch to prevent an unsafe over-heating condition.  Many times when a limit or rollout trips or opens up it will tell the furnace control board that the furnace has overheated and the blower on the furnace will run continuously to cool the furnace down until the power on the furnace is turned off and back on again. If your limit goes off again I would strongly suggest you get your furnace checked out to make sure something is not stopped up and to make sure you do not have a leak in the heat exchanger. This can be very dangerous! We sell limits and rollout switches on the following page:  Please click here if you would like to see the furnace limits and rollout switches we sell. Below we have a really good Youtube video that shows what happens when a heat exchanger or vent gets stopped up and gas flames roll out of the front of the heat exchanger. The rollout switches are placed as a safety device around the burner area to sense the hot flame or hot exhaust thus shutting down the furnace so you do not get a fire or get carbon monoxide poisoning. The video below shows an exaggerated version of what furnace flame rollout looks like. If you feel any heat coming out of the front of the furnace or if your rollout switches are going off then I would suggest calling a service company to make sure your furnace is safe. If a furnace has a leaking heat exchanger you can feel more heat come out of the furnace when the blower on the furnace starts up because a crack in the heat exchanger will allow blower air to enter the heat exchanger which creates a dangerous condition. Below we have a picture of two limits and one rollout switch. The push-button manual set rollout switch is located in the middle. We also have another really good informative video made by which shows how to replace a rollout switch. Thanks to for making this informative video! We also have another really good YouTube video made by AC Service Tech LLC that explains how to test and troubleshoot rollouts and limit switches. Thanks so very much to AC Service Tech for making this excellent video! If your rollout switch is having to be reset please call a service company to check your furnace out. If you have any other questions please feel free to email us: or comment in our comments section below. We would love to have your business!


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71 thoughts on “Problem: Why does my furnace rollout switch have to be reset so often? Why do rollouts have different temperature differences?

  1. I have a unique problem. My furnace short cycles, but only in the morning when it is recovering from the setback temperature I have programmed. During sleep, we keep the temp at 66 and then 69 at 7:00 am. The furnace has no problem warming the house from 66 to 68, but then the short cycling starts when it is within 1 degree of the set temp. This happens regardless of what set temp and setback temp I program. The house reaches the set temp within 1 to 1.5 hours even with the short cycling, and then runs fine for the rest of the day as it maintains the set temp. I’ve replaced the air filter, tried running without a filter, cleared the drained hoses, replaced the pressure switches and flame sensor. Still the short cycling happens in the morning.

    During the short cycling, I’ve observed that the fans and motors do not cut off, but the flame does. Could it be the flame roll out switch? The flame is blue and goes into heat exchanger normally, so I’m thinking it could be a faulty roll out switch, but the above symptoms have perplexed me.

    1. Hi Hugh! I would like to suggest that you make sure that if your thermostat has batteries make sure that the batteries are in good condition. Make sure that you are getting a constant 24 to 28 volts AC between the W and C (com) thermostat wires on your control board when the furnace starts short cycling. Make sure that all your safety controls are staying closed when the furnace is short cycling. Safety controls would be the limit, rollouts and pressure switch. You would need to check the rollouts and the furnace limit with a voltmeter to see if they are opening up and causing the gas to shut off. I would also recommend testing the pressure switch to make sure that it is staying closed the entire time that the draft inducer is running. If it is a flame sensing problem which I do not think that it is because the furnace is running a long time before it cuts off. Most of the time when there is a flame sensing problem the furnace burners will cut off within seconds. It would not hurt to make sure all ground wires and wire connections are good and tight. Make sure you are getting a minimum of 24 volts between R and C terminals on your control board. Low voltage can cause problems too. I hope that you can easily find and fix the problem soon! Steve

  2. I have a Comfortmaker gas heating system and the blower motor went out. Everything was running great with the system until then. I replace the blower motor with a new motor and everything ran great for 5 minutes, Then a rollback sensor went off. Is it possible that the blower is blowing tooooo hard and causing the rollback or was a weaker old blower just hiding another problem? The system is about 24 years old. Could a sensor have just went bad at the same time???

    1. Hi Mark! The rollout switch could have gone bad but unlikely. I would suggest checking (make sure you do not get burnt) by placing your fingers near the rollout that is going off while the burners are on before the blower starts up and again after the blower starts so you can test the amount of heat you can feel. You should not feel much heat around the rollout when the blower starts up. If you do feel more heat when the blower starts then I would think that you have a heat exchanger leak. Problems that could make the rollout switch go out would be running the furnace with the blower door off or have a return grill drawing air in from the same room your furnace is located. Other problems that might cause this would be a partially stopped up heat exchanger or flue vent. You could also have a cracked heat exchanger. If the heat exchanger is cracked then this could be dangerous and you would need a new heat exchanger or a new furnace. Rollouts go off usually because the furnace is not venting properly. I go over this problem in more detail on the following page: I hope you do not need a new furnace. If you have any other questions please let me know. Steve

  3. Hi Steve!

    My furnace has been acting up and your article was really helpful in understanding why. Lately, the furnace runs for an hour or so and then a switch is tripped. The furnace will then keep running the blower until I turn it off. After this I reset the flame roll-out switch and turn the furnace back on. Same thing occurs. I do not feel any heat bleeding out the front of the furnace when is running.

    I have already replaced the filter but this cycle still occurs. What should be done now? Replace the limit switch & roll-out switch? Should I test the switches with a multimeter? Do I test the switches while the furnace is running?

    1. Hi David! If you are having to reset your rollout switch ever so often then more than likely you have a heat exchanger leak or a stopped up vent. This should be checked out by a professional. You can test the rollout, but there is no real need to do this because if the rollout opens the gas to your furnace should shut off. If your gas burners are lighting then the rollout has to be closed and allowing current to flow between the two terminals. You can test the rollout either with or without the furnace set for heating to be on or off. 110-volt power should be applied to the furnace. You can test to see if the rollout is closed by using a voltmeter set to “Volts AC”. Touch one terminal of the rollout with one meter lead and then touch the other meter lead to a good ground. You should have 24 to 28 volts AC between both rollout terminals to ground. If you do not then the rollout is open and needs to be reset or replaced. The rollout could go bad and not sense the right temperature, but this would be unusual. I hope you can easily find and fix this problem. Steve

      1. Hi Steve, sadly the unit had to be replaced. The secondary heat exchanger was blocked. Sucks!

      2. So sorry to hear that David! Many times when the rollout switches have to be reset it can end up being a major problem. Thanks for letting me know the bad news that you need a new furnace. I hope you have a great and blessed New Year! Steve

  4. Hi there,

    I’ve got the same furnace and same age roughly. My issue is that the limit switch trips after the cycle is complete, never during (furnace always gets up to thermostat temp). It seems as though once it reaches the set temperature and the jets quit burning, the blower doesn’t run long enough to expel all the residual heat (cool down the heat exchanger), so the switch trips. Logically you’d just have the blower run longer than the 30 seconds it does now after the heating cycle is done. Does this make sense?

    1. Hi George! This sounds like your furnace blower is not running long enough after the gas shuts off to expel all of the heat out of the heat exchanger. On the newer furnaces, the time the blower stays on after the burners cut off is determined by the furnace’s control board. Some of the control boards have dip switch on the board where you can adjust the fan run time by adjusting the dip switches. On some of the older furnaces, the time the blower stays on is controlled by a mechanical control which can be adjusted to make the blower run longer. We discuss this type of fan control in the following post: Other problems that could cause the limit to go off after the gas shuts off would be a slow fan blower motor. I would like to suggest that you make sure that the capacitor on your fan motor is up to specs and it good condition. A weak capacitor will cause a fan motor to run slow. Also, make sure the blower wheel is clean and if you have air conditioning make sure that the underside of the evaporator coil is clean and unobstructed. Make sure that all supply and return registers are unobstructed and open. Last but not least make sure your furnace filter is clean and you do not have a filter that is too restrictive (blocks too much airflow). Most blower motors have at least 3 speeds. You might try to place the blower motor heating speed at a higher speed. I hope you can easily find and fix the problem. Steve

      1. Thanks Steve! I’ll have another look with your comments in mind. Cheers

  5. I have a Goodman propane furnace (installed in the attic) over 23 years ago. The roll out switch has to be replaced every year. Had a technician look at it 3 days ago, he found the roll out switch laying on the bottom of the furnace and reinstalled it. No screws in the switch. The tabs were bent for installion (clip like). The furnace came on, the technician left within 10 minutes and the furnace stopped again. I inspected the roll out switch finding it in place. Turned the power back on the furnace came on and went back out within 2-3 minutes. Any ideas?

    1. Hi Mr. Smith! You will need to use a voltmeter to test and see why the furnace is going out. If the furnace is burning up rollout switches then more than likely you have a heat exchanger leak and you might need a new furnace. I would like to suggest that you test and see if the thermostat is sending a constant 24 volts between the W and C (com) thermostat wires. If the thermostat is cutting off the power between W and C then this is causing the furnace to go off. I would suggest testing the safety controls to make sure they are all closed. Safety controls would be the limit, rollouts and pressure switch. Make sure they are staying closed when the furnace goes out. If your thermostat uses batteries make sure the batteries are in good condition. We have lots of furnace troubleshooting advice on the following page: I would suggest going through the troubleshooting flow chart to see what is wrong: We also have lots of troubleshooting questions and answers on the following page: If you have any specific questions please let me know. Thanks! I hope you can easily find and fix the problem. Steve

    2. Hi,
      I am getting the rollout code in the summer when I run AC. Does this indicate control board? I am also getting no power to thermostat, unless I use batteries in the t-stat.

      Was working fine until i did “maintenance” of cleaning coils outside and attempting to “fix” the t-stat (“fan only” didnt work, so I misfired it a little).

      1. Hi John! I would like to suggest that you make sure all your manual reset rollout switches buttons are pushed in if you have manual reset rollout switches. Since your thermostat is not powering up using the furnace’s transformer anymore I would like to suggest that you check the fuse on the control board if the board has a fuse and make sure that you are getting 24 to 28 volts AC between the R and C (com) wires at your furnace’s control board. If you are not getting 24 volts between R and C then you probably have a low voltage transformer problem. Make sure that none of the thermostat wires are grounding out or shorting out against one another. When you cleaned the outdoor coil maybe you moved the thermostat wires around a little and if the thermostat wires had sun-exposed dried out insulation then maybe the wires have shorted out. I hope you can easily find and fix the problem. Steve

  6. Hi, I have submitted a review of your business on all cbd stores directory but it is not showing up!

    1. Hi Heidi! I am sorry, I do not know what a CBD store is, but thanks so much for trying to submit a review! God bless you and your family. I hope you have a great and blessed day! Steve

  7. FYI, I have a 15 year old Armstrong air ultra V 90 that intermittently trips the flame rollout (I have to manually reset it). Flames look good. I still have not fixed it but haven’t given up yet and I wanted to pass on a couple of things from reading all these forums:
    1) On my furnace it is called the flame roll out switch, but it is not really. This furnace has an enclosed and sealed flame box for the burners. The flame rollout switch is a thermal switch attached to the outside of the flame box. If the flame box gets hot for whatever reason (including a flame rollout), it will trip.
    2) initially, I checked for obstructions and found 3(!) wasp nests in the flame box and in the intake vents (!) (no lectures on yearly maintenance please :-)) . Removed them, but still had the problem.
    3) Checked the gas input rate since the gas company had been installing new lines in the areas and it was with spec.
    4) After cleaning the burners, flame box, etc. , still had the problem. I replaced the roll out switch and it definitely made it better. Thought I had it fixed until we had a cold windy night. Now, I am wondering if the wind had anything to do with it. I doubt it since the flames look good and stable and it would take a lot of consistent wind to get that flame box hotter than it should be.
    5) I noticed that the furnace would not trip if running only the first stage heat (it is a two stage furnace). When the second stage was running, it would eventually trip the rollout switch. The flame still looks good (nothing impinging on the flame box) when the second stage comes on and I can hear the blower and draft inducer speed up. Don’t think it is the heat exchanger since the flame is stable when the blower comes on.
    6)Next try is to clean the light coating of dust off the top of the flame box to help the heat transfer and open up all my ducts to see if it is simply the furnace running hot and the rollout switch happening to be in the hottest part of the furnace. Though, the vents were not changed, but I am getting desperate.
    7)Next step is to see if the draft inducer is running slow, but I don’t think that is problem because there are pressure switches to make sure the draft inducer is working properly.
    8) I did notice a water leak from the air conditioner coil area above the furnace, that I have not looked into, maybe they are related somehow?
    9)I might try replacing the burners if I can find a set or removing them and cleaning them with a wire brush instead of just air.
    10)Other than that, next step is to call the service guy, but I have a strange feeling he is not going to find anything wrong either.
    If I ever figure this out, i’ll post my solution. It may take a while 🙁

    1. Hi Ron! Thank you so very much for taking the time to tell us about the problem you are having with your furnace! The only thing that I did not see that you did not do yet would be to make sure that the furnace’s condensate drain is clean. I would like to suggest if you have not already done this to take the pressure switch tubing off so the pressure switch does not get damaged and use a wet vac to suck the condensate drain line for the furnace out. Try to clean any debris and water out of the secondary heat exchanger and drain trap on the furnace. If any water is building up in the secondary heat exchanger it can partially block the vent and cause the furnace rollout to trip. Also, if you have not already make sure that the draft inducer is securely tightened to the body of the furnace so you are not getting any air leaks. The only other thing that I can think of would be if there is another wasp nest in the vent that you could not see or remove. Yes, please let us know what you find when you do find and fix the problem. God bless you for writing this so that it will hopefully help others! Steve

      1. Thanks for the additional ideas. I had already disassembled the vent system looking for more wasp nests. All clear! Inducer is tight. My current working hypothesis is that the thermal switch is just getting hot because the furnace is too hot. I checked the temperature rise (the furnace spec is 50-60 deg F, which is pretty narrow as I understand it) and it was measured at about 65. Once I went down this road, I realized that being recent empty nesters, I had closed off unused rooms and vents. I opened all the vents and rooms. I also found a setting on the furnace control board to lower the temp rise by 15 percent (increase the air flow through the furnace). So far so good! I have not been able to trip it and the temp rise is now within spec. It bothers me a little that the normal high limit switch did not trip instead of the flame rollout switch, but I image the engineers put that flame rollout switch on the hottest part of the flame box as an additional safety margin. So between the wasp nests and the empty nest, I hope I got it. I’ll post again if that was not it. Thanks for putting the forum together. It and you are helpful. Saying my prayers! God bless you too! Ron

      2. Thanks so much for your blessings and letting us know what you did to hopefully eliminate the problems. I hope your furnace keeps on working right. Many thanks! Steve

      3. Well, I thought I was out of the woods since it worked for about a week so I went and put the furnace cover back on the furnace. Within 5 minutes, it tripped again. I have noticed it works fine on stage one, but when stage two comes on, it will trip with a flame rollout switch. I watch the flame when stage two comes on and it is not “rolling out” and it looks stable but the flame box definitely gets hot. Once I realized the unit would continue to run with the flame box lid off, I watched the flame as I took the lid off and on. The flame definitely looks sharper with the lid off (it is always blue). I have double checked the intake and vent pipes for obstructions and all is clear. I began to suspect the venting may be marginal. This is the second furnace for the house and the installers used the existing venting from the previous furnace. I have the installation manual for the existing furnace and was looking at the venting length restrictions. What is not clear from the venting table is if the length of pipe is the sum of the flue vent pipe length and the intake pipe length? I would think it would be the total sum of both when looking at the table. Do you know if it is the sum of both lengths? If it is the sum of the lengths, my venting pipes are too small. However, it might be a mute point. I had the idea that since the combustion air circuit is a closed system, I should be able to measure the air flow going in the intake pipe and compare it to the outflow coming from the flue vent pipe. When I measured it, the flue airflow was 5 CFM greater(25% greater!) This makes me suspect that the heat exchanger has a leak since I checked and resealed the draft inducer. Since the draft inducer sucks the exhaust gas through the heat exchanger, it must be getting extra air from the main blower. The reason the flames look OK is that blower air is not coming out at the burners, but it simply is not sucking the heat away fast enough causing the flame rollout trip? I think it is time for a new furnace. Though if you know the answer to the venting length question, I would appreciate letting me know for future reference. Thanks again and God Bless.

      4. Hi Ron! So sorry to hear that you are still having problems! Thank you so much for taking the time to explain what is happening with your furnace. When I was doing furnace installs the length of the plastic vent pipe was the total for separate exhaust and separate combustion air. It was not a total of both the exhaust and combustion air pipes. The length of the pipe was figured on each pipe individually and not as the total of both exhaust and combustion air pipes. In the installation instructions, the instruction book would tell the installer how many feet each elbow and each 45-degree bend counted as. I had one install where I had too many 90 degree bends and the pressure switch started going off with a pressure switch error code. I had to tear the 2″ PVC vent pipe out and install 3″ pipe for both the exhaust and combustion air vent. Your furnace does sound like it probably has a heat exchanger leak since the heat is causing the rollout to trip. Sorry, you have the expense of a new furnace this time of year. God bless you and your family! Thank you so very much for your correspondence! Steve

      5. Thanks for answering my question. In diagnosing this problem I ran across a website about the myths of carbon monoxide that I thought I would pass along. I think it is mostly correct.
        I still need a new furnace, but it helped me relax a little knowing that I would most likely still wake up in the morning while I am waiting on the replacement! (I have new CO detectors as insurance as well).
        Have a blessed Thanksgiving! Lots to be thankful for, not the least of which is warm air!

      6. Hi Ron! Thank you so very much for posting this link to Carbon Monoxide Myths. Thank you so very much for your Thanksgiving blessings! Oh yes! We have very much to be thankful for! I hope that you and your family have a great and blessed Thanksgiving as well! God bless you and your family today and always! Steve

  8. My old gas furnace (Armstrong G78-100D) does not continue running. The fan motor turns on with 3 burners, runs for a few seconds, then shuts motor and burners off. What do I check? Loren

    1. Hi Loren! I would suggest that you check and clean your flame sensor. We have a post about what you are experiencing with your furnace on the following page: I hope this helps you find and fix the problem with your furnace. Steve

  9. I have read and heard many times over that a cracked or leaking heat exchanger can pose a threat from carbon monoxide. What nobody has been able to explain yet is why that is a problem when the exact same natural gas is used completely out in the open every morning and night in our kitchen? We don’t get sick or poisoned from that, why would the same gas become poison when used in a furnace?

    1. Hi Jeff! That is a very good question. The same gas from an oven has to be producing carbon monoxide. The only explanation that I can think of is that on a gas oven you have a good clean burn and many times with a leaking heat exchanger the air entering the combustion chamber of the furnace produces a toxic burn with high levels of carbon monoxide, black soot and unburned natural or LP gas occurs. I have seen this happen on some furnace that have had leaking heat exchangers or have had the heat exchanger stopped up where the furnace cannot vent properly. Many times you can see a yellow burn and the gas burners will only burn with a flame halfway back causing raw gas soot to form and stop up the heat exchanger. If a furnace’s burners are burning properly with the right gas-air mixture very little carbon monoxide will form. It is the bad burn that causes the build-up of carbon monoxide. I hope you have a Happy, Healthy and Prosperous New Year! Steve

    2. The stove in your kitchen will most certainly create carbon monoxide as well, unless it’s an electric range. Many people think that it is safe to heat their house or at least some of their living space with a big pot of boiling water on the stove, however, this does create carbon monoxide as well.

      The reason core doesn’t require the stove to have a limit switch is because someone has to physically walk over there and turn the thing on, therefore it is assumed that said person will be responsible enough to shut it back off when they are done cooking or if a CO alarm were to go off.

      The furnace requires a limit switch because it is turning off and on all night long with no one attending it.

      Many people die every year trying to heat their homes with the range (or worse yet their ovens). ANY carbon based organism WILL produce carbon monoxide once combusted.

      If you take a meter into a smoke filled bar room where a bunch of guys are sitting there playing cards and smoking big fat cigars, you will get a reading if you test CO levels.

      Run your oven and perform the same test. Next try a burner with a pot of water cooking or something. Again you will get a reading. Again, it just doesn’t contain a rollout or limit switch because the operator acts as the limit. They presume whoever turned it on will turn it off before any levels become dangerous.

      Actually, if I recall, a gas range is allowed, by law, to produce something like 800 parts per million of carbon monoxide. Now you shouldn’t be getting a reading any where near that in your home even with it running because it shouldn’t leak that much CO. Not by a long shot. You probably won’t see much more than 15ppm on your tester.

      Hope that helps.

      1. Thanks so much for your time and input, Ben! We appreciate you! Hope you have a great day! Steve

  10. The Rollout switch on my Armstrong furnace needs reset intermittently. Maybe, once every other week or so. I suspect the switch is failing and want to replace it to see if that fixes it. There are several identification numbers on the switch. I can’t find a switch matching all my numbers.
    Physically, it looks like your 1013102 ICP Heil Tempstar Rollout Limit Switch.
    The numbers on my switch are: 36TX26 L185F 6914 37520? (I can’t see that last digit on that last number without removing the switch)
    Do you have a comparable switch or can you help me identify the specs on this switch? Thanks for your help!

    1. Hi Steve! I am sorry I do not have an Armstrong parts program or a distributor who I can call to get you a part number. From looking at the specifications that you provided on the rollout switch you would need a 185-degree rollout. The 1013102 rollout that we sell is 300 degrees so I would not recommend it. I am sorry that I do not know of any of our rollout switches that are rated that low. You might do a Google search for, “185-degree rollout limit switches” and see what Google comes up with. Sorry that I can not be much help. Steve

      1. Thanks for your response. It seems like the 185 degree switch is not as common as the higher temp switches. I wonder if the previous person to work on it could have put in a lower temp switch than required. Is that remotely likely? How would I find the spec for the required switch?

      2. Hi Steve! The only way that I would know how to find out whether you have the right limit installed would be to find an Armstrong distributor or dealer and ask them to look it up using their parts program. Sorry that I do not have a way that I can look the part up for you. You might try Repair Clinic and see if they can look it up. Hope you can find someone soon. Steve

    2. Make sure CO gets measured asap!!!

  11. My heil furnace ignites for a few seconds and as soon as the igniter goes off the burners stop lighting. Then it proceeds to startup 3 times but won’t stay on

    1. Hi Gerald! This sounds like you have a flame sensing issue. I would like to suggest that you make sure that your pilot is clean and all wires, ground wires, and connections are good and tight. Make sure that the control board is fastened tight against the frame of the furnace. If you have a spark ignition then you might need a new control board if cleaning and tightening ground screws does not fix the problem. We have lots of furnace troubleshooting advice on the following page: I would suggest going through the troubleshooting flow chart to see what is wrong: We also have lots of troubleshooting questions and answers on the following page: If you have any specific questions please let me know. Thanks! I hope you can easily find and fix the problem. Steve

  12. I have a Goodman think 12 years
    They changed the ductwork to make it a dual system with a damper system, upstairs thermostat and downstairs.
    Now we try to start the heating but the light comes on 5 times so it’s a rollout switch.
    The technician is “working” but doesn’t know how to fix.
    Any suggestions?

    1. Hi William! If a rollout switch is going off the this is not good. This means that you either have a furnace venting problem or a leaking or stopped up heat exchanger. The tech needs to find out if you have a stopped up vent, possible slow draft inducer or a leaking or stopped up heat exchanger. I hope he finds a simple fix and not a new heat exchanger or furnace. Many of the Goodman heat exchangers are warranted for 20 years. God bless you and your family. Steve

  13. I’ve got a garage heater. The garage is about 19 years old, the heater is about 15. I’ve only used the heater once and for less than one hour. I shut the power and gas off to the unit and haven’t touched it since. I just sold my house and the home inspector says the unit is not working. So I turn the gas and power on and check it out. LED is doing four flashes (high limit or roll out switch). I tested the limit switch, it’s good, then find one of the roll out switches tripped, reset and everything fires right up. Within 5 minutes the roll out trips. The unit looks brand new on the inside, basically because it is. I really doubt there a heat exchanger issue, the flames look perfect.

    1. Hi George! If the garage unit has a blower that blows out air then I would suggest placing a couple of your fingers close to the rollout that is having problems and see if you get excessive heat around the rollout when the blower comes on. If you do then this is a sign of a heat exchanger crack or if the furnace is drawing return air from the garage then the return air could be causing a negative pressure and messing up the venting of the furnace. I would suggest inspecting the vent to make sure birds or wasps have not built a nest in the vent. Of course, this would create an obstruction in the vent and cause the problem you are having. I hope you do not have a cracked heat exchanger. If the furnace has a draft inducer then a slow draft inducer motor can cause this problem too. Any obstruction to the venting of the furnace. I hope you can easily find and fix the problem. Great question! Steve

  14. SOLVED: 100,000 BTU Philco updraft installed 2002 using standard filters.. Intermittent roll-out failures. After checking EVERYTHING and finding no reason for the roll-out switch tripping (even after replacing it) I surmised that my unit was simply overheating. I then opened all the registers and dampers all the way and the problem completely went away. Now the upstairs is too warm but that it better than waking up to a cold house in the middle of the night. I need to add registers so I can re-balance the system properly. When the unit was installed, one of the registers was deleted… lesson learned: They gotta breath!
    Please spread this news far and wide as many people are baffled by this problem and the only adv=ice is to look for failures (cracked fireboxes, etc. Not saying that the safety aspects should not be checked into but it seems that a lot of people do check the safety aspects and are in the same boat as I was: Intermittent unexplained roll-out switch tripping.

    Paul G. Celentano, homeowner and amateur furnace technician.

    1. Thank you so very much for sharing this information on what you learned! We really appreciate your time! God bless you and your family. Steve

  15. Bryant furnace 340mav048100ahka /oct 2003/ flame rollout switche kick out.l found two burners black and some yelow flames it looks like not enough air ,the rest look clean and blue flame ,you think i have crack heat ecchanger or is plug some burners,orifices

    1. Hi Ed! You probably either have a stopped up heat exchanger or a cracked heat exchanger. I strongly recommend that you get a tech to check your furnace out because if the furnace is not burning correctly the furnace will usually produce lots of Carbon monoxide. The silent killer. I have done carbon monoxide tests on many furnaces and when they are not burning right it can be dangerous. Hopefully the heat exchanger just need cleaning and that fixes the problem. Steve

  16. We have a carrier 48TJDO12-511. The roll out switch was corroded and wasnt able to be reset. I replaced the switch and cycled power to the system. The unit fired right up. It runs fine for a while, the burner shuts off and the fan continues to run, then the burner kicks back on etc. within a hour or so,then unit stops cycling and needs the power to be cycled off/on. nothing is tripping as far as i can tell. any ideas?


    1. Hi Rick!This sounds like it could be a control board problem since the unit quits after running a while until you power the unit off and back on. This erratic operation usually points to a relay on the control board not making good contact all the time. I would suggest checking all your safety controls like the limit, roll-outs, draft inducer, pressure switch to make sure they are working and staying closed. I see that your unit has what looks like a belt driven blower. I would suggest making sure the belt is tensioned correctly so you get good air flow. Poor air flow or if the blower motor is stopping in the middle of a cycle might cause this problem. If all your safety controls check out good and your air flow is good then I would lean to the control board as the problem. Our parts program shows that your unit uses control board part number: LH33WP003 which we sell on the following page: I hope you can easily find and fix the problem. Steve

  17. Would a stopped up “A” coil cause a flame roll out switch to trip or do I have a cracked heat exchanger? The exhaust blower is working fine and the vent is not stopped up. The unit is not going off on high limit just flame roll out.

    1. Hi Brian! No, a stopped “A” evaporator coil should not cause a roll-out switch to trip. If the rollout switch is located in the blower compartment then, yes a stopped up coil could cause the roll-out to trip. A stopped up coil could cause the furnace to go off on limit. If the roll-out switch is located around the burners and if you feel more heat around the roll-out switch when the blower starts up then more than likely you have a heat exchanger leak or a stopped up heat exchanger. I would have this checked out immediately because this can be dangerous to you and your family.

  18. Hello Mr. Arnold!

    So I had a question I am hoping to find an answer to. I just had a warranty company send a guy out to replace the gas valve on my Carrier furnace. But before I call them again for this next problem, I wanted to see if hanging that gas valve (and subsequently not adjusting it properly) would cause a Code 33, or the rollout/limit sensors to trip? I have 3 on this furnace. The main rollout/limiter then two others with reset buttons. The resets were not triggered. The main sensor is just behind the gas valve. It runs fine intermittently but other times it will trigger that code 33.

    Any tips?

    1. Yes, if the new gas valve they installed is not adjusted properly it will cause too much input gas which could over-heat the furnace and cause the limit to open. I would suggest that you call the company back out to solve the problem. It is not good for your furnace to be going off on limit or a roll-out opening up. Steve

  19. I am having a problem with my roll out switch and I replaced it and the furnace ran for about 10 or 15 minute and the second led light started blink three times again. I believe before I buy a board I am going to make there is no obstruction in the vent. Then I will change the pressure switch and the board will be the last result. Hopefully I won’t need a board.


    1. Hi Cwhazz! If the rollout switch is going off within 10 to 15 minutes then, yes I would suggest making sure that the vent is not obstructed. I would suggest, if possible to place your finger near the roll out switch that is going off and see if you feel more heat come out around the rollout switch when the blower kicks on. If you feel more heat around the rollout switch when the blower kicks on then more than likely you have a heat exchanger leak and you will either need a new heat exchanger or a new furnace. I hope that you do not need a new heat exhanger or furnace! If the heat exchanger is leaking then this is not safe for you or your family (can produce carbon monoxide poison) so I would suggest getting the furnace fixed as soon as possible. If I go to a home and find a heat exchanger leak here in Louisville, KY. we are instructed to turn the furnace off by turning the gas off until it is fixed. If your pressure switch is acting up too. Then I would suggest cleaning the draft inducer out and make sure the hole where the pressure switch attaches to the draft inducer is unobstructed. If you have a condensing furnace then make sure that the water drain on the furnace is open and not stopped up because this will cause the pressure switch to not close and work properly. I hope you can easily and inexpensively find and fix the problem. Steve

  20. I have a packaged unit that keeps throwing a roll-out fault however when I remove the front access cover the burner seems to run fine however with the cover on I can hear the flame rumbling and igniter relighting the gas. Why would the cover off allow it to run better?

    1. Hi Mr. Johnson! This sounds like the burners are being starved for air when the access cover is on. This could be caused by a partially stopped up vent system, heat ex-changer or a leak in your heat ex-changer. A slow running draft inducer that is not pulling enough draft could also cause this problem. This can be dangerous so I would recommend getting it checked out by a professional if you can not find the problem. I hope you can easily find and fix this problem. Steve

      1. Ok, I just posted a question and then saw this. I noticed this with my furnace too. It ran better and didn’t throw that 33 Code with the cover off.

        One thing I noticed was that the furnace filter doesn’t sit all the way in the slot. About 2 inches or so hangs out. Would that be causing an air leak that would make the system throw a 33?

      2. I really do not know what a “Code 33” is but I am guessing it means the furnace when off on high limit. No sir the filter hanging out 2 inches should not cause the furnace to over-heat. If the filter is too restrictive or too dense then then this could cause the furnace to over-heat. I hope you can find the problem. Steve

  21. Hello I’m having a problem with my gas furnace, model #54192110. The relay switch keeps popping out, I go down and hold it for 30seconds then it comes back on. I thought maybe it could be the thermostat because it is a very old furnace, so I was thinking if I changed the thermostat it might help problem. Can you please help me with this problem

    1. Hi! If the rollout switch is popping out then you either have a bad rollout switch or a stopped up heat exchanger or a leaking heat exchanger. If you feel heat coming out around the rollout switch when the burners are on and when the furnace blower starts then this is a sure sign that you have a leaking heat exchanger and this needs to be taken care of imediately. I would strongly suggest that you have a professional take a look at your furnace to make sure it is safe to operate. Rollout switches are safety controls and this could be telling you the furnace is unsafe to operate and needs to be repaired. Sorry for the bad news. I hope the furnace just need cleaning and this takes care of your problem. I hope you can easily find and fix the problem. Steve

  22. I’ve found excellent advice here; thankyou! I just installed a nordyne (propane) and the open limit switch trips after about 7 minutes of operation. There appears to be no blockages. Any suggestions? Could it be too hot, and should I turn back the gas? Thankyou for your advice!

    1. Hi Mark! Please make sure you have the furnace door installed and nothing in the house is making a down-draft in the furnace. I would test (feel with a finger) around the rollout switch that is tripping for a few seconds to see if the switch is getting too much hot air around it. If you feel not much heat when the blower is off and then more heat when the blower comes on then this is a sign the furnace has a heat exchanger leak and needs to have a new heat exchanger or a new furnace. I hope the heat exchanger is not the problem. I do not recommend adjusting LP gas furnaces because it is so critical to get the right fuel air mixture for LP to burn and ignite properly. You might have a tech in who is experience with LP gas to adjust your furnace. Please make sure the exhaust heat is going up the stack and not out into your living space. If the furnace is not venting properly this could also cause this rollout switch problem. I hope you can find an easy inexpensive solution. Steve

      1. Thank you! I will check that out.

      2. I have a goodman unit when I push the button on the roll out switch it will not run long then when it try’s to light all u can here is the ignighter trying to light but it will not light it try’s but u haft to push the button again to get it to light

      3. Sounds like you have a bad roll out switch or your furnace has a leaking heat exchanger or a stopped up vent. You should never have to reset a roll out switch unless there is a problem with the furnace. If you feel heat around the roll out when the blower on the furnace comes on then I would say you have a cracked heat exchanger. This can be dangerous. I would suggest that you have your furnace checked out for a cracked heat exchanger or stopped up vent system. Steve

  23. I’m having problems with my limit switch cutting on and off I can unplug one element and in a run-on 5K good but it won’t run on 11.6 for some reason

    1. Hi Mr. Gasaway! This sounds like you are having an air flow problem. Not enough air is getting through your air handler to keep the limit from going off. Low air flow could be caused by a dirty filter or using a filter that has too high of a merv rating and is restrictive. Low air flow can also be caused by a dirty or partially stopped up evaporator coil, a slow blower motor (make sure motor capacitor is in good shape). Also make sure your return air is not obstructed or your supply air is not obstructed. I would suggest opening all supply registers so air flow is not restricted. Please make sure that the heaters are going off when the thermostat is calling for no-heat. A stuck-ON heating element can cause a limit to open. I hope you can easily find and fix the problem. Steve

  24. Real easy on a natural draft furnace as compared to a high effect unit to check be careful what you tell people. Service tech for many years. Dealing with people that know what there problem is because they saw in on-line.

    1. Thank you for your input on this topic Mr. Hillier. I hope you have a great day!

      1. Thanks . Another question. It blinks for pressure switch closed too. How can a furnace have two problems? I replaced the high limit and rollout switch. Trying. Determine the reason. No flames coming out of the area.

      2. Hi Ms. Jackson! When parts malfunction on a furnace it can create multiple problems. For example if the draft inducer is not working right it will cause a pressure switch fault. If a blower motor is not working it can cause the furnace to go off on limit and the air conditioner coil to freeze up. If your furnace has a stopped up heat ex-changer or a leaking heat ex-changer it can cause the limit to go off and rollouts to trip which causes the whole furnace to shut down. I hope you can easily find and fix your problem. Steve

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