I have a 2018 Terry Classic 21 trailer with a Dometic/Atwwod AFMD 30121 forced air furnace. Recently, I turned it on and cold air blew but the burner never came on. I checked the propane and it was turned on. I tried several times, but nada. So I took out the furnace (not easy!) to pull and clean the sail switch, which appears to be functioning. With the furnace out of its cubby, and with the hoses disconnected, but the exhaust pipe inserted, I am getting 12V at the thermostat and to the furnace itself. But now the blower doesn't come on. The circuit board has an LED, but it is not lit, even though I have confirmed that the board itself is getting 12 volts. Is there a sequence for troublshooting these things? Do I need a new circuit board? Is there an interlock switch that keeps it from functioning when it is removed from its housing? This is my first attempt at repairing a furnace, but I have some electronics skills. Any and all suggestions are appreciated.
