Originally Posted by Harley97
I have a 2018 Thor 24HE. The Atwood heater does not want to work. When I turn on the heater the fan comes on and sometimes I can hear the heater attempt to fire. Other times it doesn't even try.
I have propane flowing. I have tried lighting the heater while the stove is running and after running the stove with no luck.
I checked the sail switch and it is as clean as a whistle.
Any other ideas?
Your description of spark attempts sometimes and not at other times sounds like a loose or poor electrical connection in the fan proving circuit of the furnace. Your guess at the sail switch is a good start. The fan starts when there is a call for heat, so the 12vdc is OK and the thermostat is calling for heat OK. The proving circuit “usually”consists of the sail switch in series with the high temp limit switch connecting to the control board. If the proving circuit fails (open/bad connection) no sparking attempt will occur initiated by the control board. Check your proving circuit wiring connections are clean and tight in the furnace. Worst case it might be something strange like a crack in the control board copper trace that opens/fails sometimes and works other times. A multimeter to test the various proving circuit components might come in handy if you visually can’t find the bad connection.