Confusing furnace

[OddOne]

Hi everyone maybe you can help. We have a 82 Tiffin allegro with a 30,000 BTU furnace. im gonna do my best to describe what it does(furnace), when you turn the thermostat on you can hear the blower kick on then a couple seconds later hear the flame ignite. after a while the flame will cycle off for a little then kick back on and does this till rv is warm. but every now and then you can hear a poof when it lights but usually lights. sometimes it don't even sound like it tries to reignite(maybe it does) usually Im busy working of things. but i check the the thermostat and the connection is made inside the thermostat and blower is running but just cold air blowing. If i turn thermostat off then back on it ignites and is good again. what i cant figure out is why it fails to reignite. don't know if this will help but driving down the road furnace wont light. Propane tank is full Stove, oven, and fridge all work on propane.(haven't installed water heater yet sitting on desk at the moment) owners before caped off the line at T. If you need anymore info Just ask and ill go find out.
Thanks,
Chris

[Sprdtyf350]

I had one acting like that recently. It had a Mud Dauber nest in it causing it to run for a while, and then shut down.

It was also picky about wanting to relight. Turned out the ignitor would occasionally spark to the outer case instead of across the gap inside. Cleaned the ignitor, put some high temp rtv on the terminals where the leads attach and it has been good to go. The gap on the ignitor also needs to be the correct distance so the unit can tell it has a flame.

I would suggest that the unit get removed, and cleaned. You really can't get everything out of the burner case while it is still installed. I took mine all apart and was shaking chunks of mud nest out of it.. That was after I had cleaned it once before. Guess the baking for a while as the furnace ran loosened the rest up..

[OddOne]

I can see the mud dauber issue. I've been finding them everywhere doin this renovation. Even inside the rv itself. I just don't think they could get in furnace. (see pic). The screen should keep em out. (was there when got rv)