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Why is my RV furnace cycling? T-stat OFF

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Why is my RV furnace cycling? T-stat OFF

Old 11-02-2020, 10:09 AM
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Default Why is my RV furnace cycling? T-stat OFF

I have a 2018 Forest River 5th wheel. I know itís built like shit. They all are except for Luxe. I understand that. The fan on my furnace has been cycling for a couple minutes on the hour for the last couple days. Itís not attempting to light, just running the fan. The T-stat is off. There is gas in the tank, so thatís not keeping it from lighting. The ignition doesnít even engage (it makes a loud clicking sound when engaging so itís easy to know when it is/ isnít engaging). Iím glad itís not lighting- donít get me wrong, I just donít understand why the fan is cycling when Iím not asking it to. ??? Any ideas?
Old 11-02-2020, 10:12 AM
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make sure in fan mode the thermostat is set to auto
Old 11-02-2020, 11:31 AM
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Originally Posted by DLG4354 View Post
I have a 2018 Forest River 5th wheel. I know itís built like shit. They all are except for Luxe. I understand that. The fan on my furnace has been cycling for a couple minutes on the hour for the last couple days. Itís not attempting to light, just running the fan. The T-stat is off. There is gas in the tank, so thatís not keeping it from lighting. The ignition doesnít even engage (it makes a loud clicking sound when engaging so itís easy to know when it is/ isnít engaging). Iím glad itís not lighting- donít get me wrong, I just donít understand why the fan is cycling when Iím not asking it to. ??? Any ideas?
There may be gas in the tank,but the regulator at the tanks may not be delivering gas. Light up the oven and make certain the pipes in your rig are full of gas. Same with water heater.
If you have gas at the oven, then you likely have gas at the furnace also.
Our furnace and fridge wouldn't work and the thermostat was dead yet the lights were on. Silly me. Lights are powered by the D/C battery. Checked plug and noticed we were without A/C power. Reset breaker and firmly plugged in the unit and everthing including the T stat started working.

Long shot. D'C all power to your unit including the d/c battery and rehook up everything. Essentially reboot the thermostat with a hard electrical reset.

Otherwise, I got nothing.
Old 11-02-2020, 12:16 PM
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is this the main blower or the purge fan that is coming on and off?
Old 11-02-2020, 12:46 PM
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Originally Posted by 99yam40 View Post
is this the main blower or the purge fan that is coming on and off?
I suppose itís the main blower because itís coming out all the heater vents.
Old 11-02-2020, 12:56 PM
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Originally Posted by DLG4354 View Post
I suppose itís the main blower because itís coming out all the heater vents.
then it could be the stat telling the blower to run, or the fan wire is shorting to a power wire.
I am not sure how the ones in RVs work,
but in a home unit the gas furnace is lit and heats up the heat exchanger before the fan kicks on by a fan thermal switch.
that fan switch or stat could be turning the fan on and off.
a good voltmeter, wiring diagram, and some knowledge should point you in the right direction
Old 11-02-2020, 01:17 PM
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Originally Posted by 99yam40 View Post
then it could be the stat telling the blower to run, or the fan wire is shorting to a power wire.
I am not sure how the ones in RVs work,
but in a home unit the gas furnace is lit and heats up the heat exchanger before the fan kicks on by a fan thermal switch.
that fan switch or stat could be turning the fan on and off.
a good voltmeter, wiring diagram, and some knowledge should point you in the right direction
RV gas fired heaters work the opposite. The fan starts first and runs for 15 seconds before the gas valve and igniter are fired, neither of which will happen if the sail switch doesn't detect airflow or the overtemp disc detects too much heat in the exchanger.

If the fan is cycling regularly, and the thermostat is indeed off, it's likely a failed thermostat and quite common. They're cheap and a generic battery powered one from the box stores works just as well for $20. Unless you have a two-speed Hydroflame that is (like my current heater, those take a little modification to make work, especially with a Dino board!
Old 11-02-2020, 01:35 PM
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Did rain or water get in their? Mine was turning on and off. Turns out that I washed the camper and evidently got some water in their and it was shorting out. Turned leaf blower on for awhile and used it to dry things out. Solved the problem
Old 11-02-2020, 02:04 PM
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Mine was doing the same thing-replaced the thermostat and still had the problem.Replaced the cheap chinese made circuit board and that fixed it
Old 11-02-2020, 02:43 PM
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Originally Posted by waynesworld10 View Post
Mine was doing the same thing-replaced the thermostat and still had the problem.Replaced the cheap chinese made circuit board and that fixed it
Which circuit board? In the furnace?

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