Trouble with Atwood furnace not lighting?

[JGFlack]

We turned furnace on and the fan comes on and you can hear the unit cycling but will not light. We have never used the furnace but had the interstate serviced and a once over (it worked then but it was hot middle of summer). Does anyone have any suggestions to what we should check? Thanks in advance. (Propane is full). 2006 Mercedes Frieghtliner interstate.

[MountainLife]

Our process is:
Propane switch on outside of AI turned on
House power turned on
Set thermostat to FURN
Adjust thermostat temperature up above current inside temperature

Sometimes it takes a bit if the furnace has not been used in a while. It takes time for propane to fill the lines. Does your cooktop light?

We’re on our first road trip of the new year and will need our heat tonight.

[Rocinante]

Assuming there’s plenty of propane, it’s on, and the stove burners light properly, the furnace’s sail switch is the most common reason for a furnace not lighting. It’s an inexpensive part, and if you’re handy, you can probably check this switch and replace it if needed.

[WhatNext]

A couple related problems in the first year of our 2021 19' Bambi:

1) The flex hose connecting the propane supply to the furnace got kinked. The furnace would start blowing but not ignite then shut down

2) The outlet temp of the tankless hot water heater started going lower and lower. Flame was blue and even. Stove and furnace were working. Thought the worst but the whole hot water heater would have to be pulled out to get at anything. Even looked at getting the AS into a dealer but the waiting time was at least a month (we were on the road). Then the furnace stopped igniting. Ha Ha, a propane supply problem! Regulator bad? Turned out that turning the tiny flow adjustment screw (under the regulator) open a half turn got everything working! Will keep an eye on it.

[wlrhoads]

Had the same problem. It was the sail switch, we now carry a spare. Also after you try the furnace check the circuit board for the error message. It is displayed by a flashing LED.

[Boxite]

Spider webs/nests can wreak havoc on burners by disrupting proper air-flow. A long bristle-brush run up the flue followed by a blast of compressed air can fix things…just don’t damage a sail-switch if you run the brush through. (This solution is particularly applicable to the water heater.)

[JGFlack]

Thanks everyone for your suggestions. It turned out to be a dirt dobber nest that was built wayback in the exhaust pipe. It actually had a perfectly balanced pattern to it and was so far back we couldn't see it. Hubby removed it and it fired up, yay!

[StogieMan]

For those of you with Interstates with the Atwood furnace and if you’re looking for the sail switch - here is the location.

The bad news is that it’s located way in the back of the furnace with very little access. I looked in between and there is no access panel built into the side of the furnace nor did Airstream provide one on the opposite where the bottom freezer is. I looked all around on both sides and the outside. The right side where the big access panel is behind the table storage will not get you access. I pulled out the exhaust vent to see if maybe there would be access but I did not get far as there is only the cutout holes for the vents and no way that you can get to the sail switch from here to replace it.

The only way that I can see is by unscrewing the furnace and puling it out. This will require you to unplug the propane line on the right side which is easily accessible. So this where Airstream will be charging you big bucks for their time and not the easy part of replacing the switch.

I’ve been doing some work in the van and the furnace was not cutting on and off at the desired temperature so I dug into this and it was the sail switch that had some dust and lint around it. I got creative with a long screw driver, a makeup brush and a straw cleaner and was able to get it cleaned up. I’d recommend that you do the same to avoid any issues down the road and put this on a regular maintenance list.