Heater problems
The #1 cause of a furnace not lighting it the sail switch(probably the door mentioned in previous post). The sail switch is in the circuit to the gas valve and if the blower does not move enough air for the furnace to operate safely, that switch does not close and the gas valve does not open. Exactly how the switch is in the circuit depends upon the make and model of the furnace. But the most common cause of the sail switch failing to close is low voltage, if you are operating on the RV's battery. Low battery voltage means that the blower truns more slowly and less air moves, thus no closing of the sail switch. If voltage is 11V or more at the motor, then that isn't the problem. Wasp nests are a common problem that restricts air flow as well. If the air movement was minimal, it would be possible to have the furnace light, then go off because the switch opened again. It is possible that the ignitor is bad, but that could be checked by lighting the flame with one of those butane gas grill lighters. If there is gas there, that will make it light. If it lights, and then goes out every time, that means that the flame sensor has failed, but on your furnace you probably have a seperate sensor from the ignitor probe, so it isn't likely that both have failed. Low gas pressure could also cause this problem. Gas pressure should be 11" of water column measured at the furnace. The ignitor circuit board could cause it, but not likely. The same is true for the over temperature limiter. To trouble shoot this problem you really need to have a good meter, and some knowledge. You could just start replacing parts, but you might replace a lot of expensive parts and never find the real problem.
:laugh: 