It's interesting that you would post this question at this time. Our furnace went out last night. When a tank runs out of propane and I switch over to the other tank, or get a tank refill, it has always taken my Dometic 36,000 BTU furnace to fire on the 3rd attempt. After that, it runs OK. Except last night/this morning.
At work I did a little searching and remembered this thread from just a few days ago and subscribed to it so I could read through it more careful later, which I did a bit earlier.
Click here. Lots of suggestions what could be wrong.
I called my dealership and found out the earliest I could come in for a repair would be the second week of December, so I was determined to figure this one out myself.
On the way home from work, I thought about it, rather disappointed at the long wait time for a repair. And by now, I read every word on that thread linked above.
I thought to myself, well... it don't work right now, the most I can do is fiddle with it and hope I do something right. Otherwise, December is a long wait!
I got home and removed the outside cover and found a LOT of dirt (loose stuff) and bugs in the bottom of the furnace compartment. I got my leaf blower and blew the stuffings out of everything. It was then I noticed the rocker arm (reset) button, and thought to my self? Why not. I flipped it off and back on, turned the thermostat back on and wholla! It fired up ... first time!
I let it run and cycle a couple times, took some pictures, and put the cover back on as we're expecting rain tonight. So far, so good.
Diving in and just doing a good cleaning and blow out, just saved me a month of agonizing wait, and maybe a couple hundred bucks for 5 minutes of work, and flipping a switch off and on!
Pull your cover, see if there are bugs and spiders in there. If so, blow it all out, see if that helps. Do the easy stuff first, progress to the harder stuff mentioned in the other thread in ascending order if difficulty and expense.
