Furnace doesn't light

[Coach Mac]

The furnace doesn't light. The blower comes on but no ignition.
This happened two nights ago and yesterday I removed the panel under the refrigerator and was able to reach the switch on the top of the heater. I reset it and the blower and furnace came on. This morning the furnace was off again but hitting the reset switch didn't work.

I checked the fuse and it is good. There is propane coming to the stove so it doesn't look like a fuel supply issue.

Any ideas?

[jsb5717]

It would help what trailer you've got and what year it is.

Generally I would first suspect the sail switch. That switch must engage before the furnace will attempt to ignite. You've got the fan spinning up but now sparking, right? As a test you can jump the 2 wires connected to the sail switch, set the thermostat to call for heat from the furnace, and see if it attempts ignition.

[ChuckS]

Originally Posted by jsb5717

It would help what trailer you've got and what year it is.

Generally I would first suspect the sail switch. That switch must engage before the furnace will attempt to ignite. You've got the fan spinning up but now sparking, right? As a test you can jump the 2 wires connected to the sail switch, set the thermostat to call for heat from the furnace, and see if it attempts ignition.

Normally the controller module will see that the sail switch circuit is closed when it shouldn’t be and the blower motor will not spin up because of that jumper wire

It’s a Dometic Atwood furnace the OP is working on.. Suburban furnaces doesn’t have a switch on the outer case..

I would remove the sail switch and blow it out with compressed air and then put a multimeter across the sail switch leads and move the paddle arm

Should read less than 1 ohm resistance with paddle arm one direction and then infinity with paddle arm moved the other way

[ChuckS]

You can however follow these steps and temp jumper the sail switch wires after the blower motor spins up