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Old 09-17-2021, 07:16 PM   #1
Junior Member
Brand: Thor Motor Coach
State: Michigan
Posts: 11
THOR #15979

I have a 2018 Thor ACE 27.2,
The furnace has been intermittent. Won't work at all now.
I believe it's an Atwood. It's getting 12v. The switch is ok, the thermostat
works on AC, it has gas and the gas valve is on. I pulled the side vent and
cover to check for bugs and loose wires. When it was working the blower
would come on first then the furnace would light and it would get warm.
Any ideas or what you did to fix yours ?


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Old 09-18-2021, 01:35 PM   #2
Senior Member
OldWEB's Avatar
Brand: Thor Motor Coach
Model: 2011 FW Hurricane 33T
State: England
Posts: 1,158
THOR #16471
Sounds like you narrowed it to the furnace, now you need a multimeter and know how to use it.

Maybe it needs a "thump"? Good info and links here.
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Old 09-18-2021, 02:11 PM   #3
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16ACE27's Avatar
Brand: Thor Motor Coach
Model: ACE 27.1
State: Florida
Posts: 12,739
THOR #7035
Two issues with Atwood furnaces:

1 - The control board easily gets wet and won't work until it dries out.
2 - The control board goes bad.

Since the A/C and thermostat work then you are getting 12 VDC to the control board - verify the ON/OFF/RESET switch for the furnace is in the ON position.

If you don't even get the fan running when heat is called for it is most likely a control board issue although it could be a fan issue. The furnace will not attempt to light unless it sees the fan is running by the sail switch.

Replacing the control board is a DIY project and I highly recommend you use the aftermarket Dinosaur board instead of the OEM replacement board.
Ted & Melinda
2016 ACE 27.1
2016 Chevy Sonic Toad
2020 Chevy Colorado Z71 Trail Runner Alternate Toad
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