Furnace Problem and Solution
I had a problem in August when I tested my Atwood 8535-IV DCLP furnace, and today I had the same problem. Previously I fired up this propane furnace anticipating that I would need it some time over the following 2 months and it kept shutting of after about 60 seconds. The blower cleared the firebox for about 15 seconds, I got heat exhausted for about 5 seconds, then no heat for 5 seconds, then heat, no heat, heat, and then the furnace shut down and refused to run any more. I took the cover off, checked connections, blew out some dust, scratched my head, and tried it again and it was fine. And it worked fine when I needed it on that trip.
Fast forward to today when I took the Montana from storage and I had the same problem. Except it refused to work correctly no matter what I did. I took apart the blower, checked all the connections, and tried it again with the cover off. Same result. I noticed a blinking red light on the control board. Three red flashes, pause, then repeats, which means "Ignition lockout Fault". No clues in the owners manual on what this means, and not much in the manual for trouble shooting.
So I got on-line and googled "Ignition lockout Fault on an Atwood 8535-IV RV Furnace" and found lots of info. It was not the sail switch or a fuse. I was almost ready to order a new control board for $100. But one of the forum entries said that this error message could result from low propane pressure or air in the line.
There are a number of causes for these and some of them are typical of taking your camper out of storage. Turning on the propane too fast after being shut off in storage is a big one. This partially trips the runaway prevention valve on the propane tank. I fired up the stovetop burners and let them run for 10 minutes. I got excited because they were hard to light and there was air in the line, and the flame pulsed slightly (which I don't think it normally does). But it didn't fix the furnace problem.
Another solution is to shut the tanks off, and take the lines off the tanks, and then reconnect and s-l-o-w-l-y open the valves. If the runaway shutoff valve is partially tripped it would reset itself, and this solved my problem. It only took all afternoon, but at least my pipes won't freeze overnight. (Did I forget to mention that I purged the antifreeze from the water lines BEFORE I tested the furnace?)
Other solutions that worked for users in the forums were replacing the propane regulator because it might be bad, and replacing the control board.
I think it all comes down to inadequate propane flow, or maybe a bad control board erroneously sensing inadequate propane flow. I spent about 5 hours on this today and was really frustrated, but now it's fixed.
John & Janet from Connecticut
2012 Keystone Montana 3150RL
2012 Ford F350 Diesel 4x4 Lariat Crewcab SRW