Atwood Furnace Shuts Down in 90 Seconds

[Baja937]

This past weekend I wanted to prep for fall camping and wanted to check out the furnace for operation. It's a 2014 Lacrosse with an Atwood furnace and Dometic Single Zone LCD Thermostat. No Heat Pump or Strip. A/C works fine. I believe it's the 8531 30,000 BTU Model.

Fan in Auto. Furnace selected. Thermostat temp increased well above interior temp. Blower kicks on and begins normal cooler air flow. After approx 90 seconds the blower and furnace shut off never supplying warmer air. NO Error Code. 2 full 30lb tanks with valve open.

Any ideas? I can't find any T/S for this online.

[n7bsn]

First thing that happens is the fan starts
The activates the sail switch
Which opens the propane valve and sparks the ignitor.
If there is no heat detected the furnace shuts down.

Could be: sail switch, propane valve, ignitor, thermocouple or controller board. Oh, ya, and no propane.

[newman_fulltime]

do you have your propane on?

[downtheroad]

If the blower runs, but the furnace doesn't ignite and then shuts down - that sounds like the sail switch is stuck or has failed.

The sail switch is an on/off device. (normally in the off position) It gets it's name from the "sail" or paddle that is attached to the switch mechanism. As the blower comes up to speed, it blows air onto the sail with enough force to push the switch closed, thus allowing electrical current to flow to the next component in line.

It's job is to determine if there is adequate air flow for proper combustion to take place. If the battery voltage is low or the fan does not come up to 75 per cent of it's design speed, the sail switch will not close.

Possible causes of this malfunction are: low battery, restricted return air inflow, restricted or inadequate outlet vents, restricted combustion air inlet or exhaust, faulty sail switch.

[Baja937]

I'm hearing it...Like an idiot I waited to check it just before I was ready to leave Sunday...Therefore I haven't done anything yet...

Hopefully It's as simple as the dreaded wasp/mud dauber nest...It worked fine this spring...

[dave17352]

Do you hear the igniter try to fire the furnace. If so and you never hear the furnace fire perhaps you need to purge the line. Let it cycle a few more times. Also how about closing and reopening the tanks very slowly because if open to quickly they can cause the propane lines little safety do dads to kick in and close off the flow of propane. JMHO