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

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

Answer:  The rollouts switchs and limit 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 over-heated and the blower on the furnace will run continuous 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 real good Youtube video which shows what happens when a heat exchanger or vent gets stopped up and gas flames rollout 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 poisioning. 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 real good informative video made by RepairClinic.com which shows how to replace a rollout switch. Thanks to RepairClinic.com for making this informative 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: support@arnoldservice.com or comment in our comments section below. We would love to have your business!

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

  1. 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

  2. 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

  3. 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

  4. 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?

    thanks!

    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: https://arnoldservice.com/product/lh33wp003-carrier-bryant-furnace-control-circuit-board/ I hope you can easily find and fix the problem. Steve

  5. 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.

  6. 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

  7. 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.

    Cwhazz

    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

  8. 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

  9. 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

  10. 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

  11. 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

  12. 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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