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Old 05-24-2022, 12:29 PM   #1
Guy from Cowtown
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Furnace cycling off and on frequently

Hi everyone. We are a 2020 3120RL. Our furnace has started cycling on and off frequently, i.e. kicks in, runs 10 seconds then cuts off for 10 seconds, on 10-off-10, and just keeps repeating until it reaches the desired inside temperature (at least we're warm) but its annoying as heck at night. I think I might have replace some kind of heat/ temp sensor or board? Anyone else ever have the same problem? Thanks in advance!!
 
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Old 05-24-2022, 02:25 PM   #2
Bourbon County
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Most of the furnaces have 2 different fans in them. One is a draft induction blower that supplies air for combustion, this is the first thing you hear when the furnace gets a heat call. There is an air flow sensor for this blower to prove you have combustion air; these are a pretty common failure point and fairly easy to replace. If the furnace is actually lighting the burner, this is not your problem; the burner won't attempt to light without proof of air flow. There is a timer that will time out if you don't get air flow confirmation.

If the burner is lighting and then cycling off pretty quickly, it could well be a flame sensor. The mother board is another possibility, but I wouldn't think likely if it starts the ignition cycle and the main blower comes on. The other fan is the blower that actually circulates the warm air.
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Old 05-24-2022, 04:12 PM   #3
jsb5717
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Could be a few different things. Could be the air flow sensor as stated above. It could also be your propane regulator. Ours was acting similarly until I replaced our OEM Fairview regulator with a Marshal Excelsior regulator. Less likely, it could be your thermostat. If it's a Dometic they can be finicky.

The fact that it's actually completing all of it's pre-ignition functions and firing before shutting down would point me toward the regulator
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Old 05-24-2022, 04:35 PM   #4
Carl n Susan
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Not having a newer furnace and not knowing exactly when this came about, but there have been numerous reports that the cheap, poorly made, inferior, 15 amp self-resetting fuse for the furnace may cause this problem. Change to a standard blade fuse and the problem goes away?
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Old 05-25-2022, 09:09 AM   #5
Bourbon County
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A quick easy check you could do is remove the exterior access cover and check for obstructions in the supply and exhaust. These areas are subject to obstruction by insect nests, leaves, and even sometimes small birds. This is the air path for combustion air and if they are restricted, I doubt you would get the airflow switch to make and the burner would ever fire.

Have you actually measured the 10 second intervals you mentioned, or is that just a guess? When the circulation blower comes on do you hear any unusual noises like a squealing sound? They use sleeve bearings in those motors and they tend to get pretty loud when they fail. A blower motor bearing failing might be enough to overload and drop out.
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Old 05-25-2022, 02:33 PM   #6
steiny93
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could be tripping from the 'high limit switch'

When it cycles, does the fan continue to run but the burner is cycling? Or are you saying that the fan in cycling (stopping and restarting)?

If the fan runs continuously but the burner is cycling it could be that the switch is bad or you have an obstruction in the air way.

I'd recommend starting by verifying that all the ducts are opened and not restricted, it's common to have an air restriction cause this type of behavior, very common with fish houses.
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Old 05-25-2022, 03:40 PM   #7
Arkware
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I second Carl's suggestion. The 12 volt re-setable fuse.
Had trouble with mine and replaced the fuse with a 'standard' fuse.
no trouble since.
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Old 05-26-2022, 06:53 AM   #8
Wisconsin Retiree
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Not to change the subject but out of curiosity how loud are your furnaces? Aside from very noisy inside the trailer when I am outside my furnace sounds extremely loud to me? The guy next site even commented how it sounds like an industrial size furnace??? Are others as loud?
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Old 05-26-2022, 08:06 AM   #9
jsb5717
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Quote:
Originally Posted by Wisconsin Retiree View Post
Not to change the subject but out of curiosity how loud are your furnaces? Aside from very noisy inside the trailer when I am outside my furnace sounds extremely loud to me? The guy next site even commented how it sounds like an industrial size furnace??? Are others as loud?
They're all loud. Some have said that the Suburbans might be a little quieter than the Atwoods but they are still loud. There are also different BTU furnace sizes, which will likely have show variable in volume. Ours is surprisingly quiet indoors, but that's due to placement and insulation between the furnace and living space. Outdoors ours still sounds like a blast furnace.
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Old 05-29-2022, 03:48 PM   #10
Denali
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Sometimes its because the furnace is not getting gas. Turn on your gas stove and your gas hot water heater. Let them run and then try out your furnace. Also check your battery as the furnace get 12 volt power to operate. I try little things first
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Old 05-29-2022, 09:04 PM   #11
DaveK
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We had the re-setting fuse problem as well.

We also had the control board replaced under warranty.
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Old 05-30-2022, 09:30 AM   #12
nellie1289
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This is a timely post for me as well. We are out in our 2021 this weekend and i seem to be having similar issues. We have never really used our furnace before as we only go out in summer but it has been chilly here in the northwest. i do check the furnace exahust for pets and run it once in a while to make sure there is no issues. I put the thermostat to "heat/Electric" and the gas furnace definitely fires. You hear a fan kick on, then the furnace fire, then it blows heat for about 1 minute. The heat pump seems to turn on too. Then about a minute later it turns both off, and then both come back on and the process continues as the temperature slowly comes up. I have no idea what is wrong.

Also how come my thermostat sometimes shows "heat-gas" "heat gas-electric" and some times "heat-Electric". What im saying is sometimes "heat-electric" is not one of the toggle options.

I have the coleman airxcel thermostat and heat/pump air conditioners
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