There is NO way to work on your model without pulling the complete furnace. I would be inclined to suspect the hi limit switch rather than the sail switch. Hi limits(Atwood) are common (for service people when under warranty) to fail. They "stick". If you suspect your sail switch, a quick way to test is when it fails to light, gain access to the inside furnace casing and bang on it. If the sail switch is sticking(very rare) this may free it up. Of course banging on it may unstick the hi limit also. If you are going to do the work yourself, then replace both the sail and hi limit switch. Doug
