Furnace trouble

[tcowen]

Have a 2006 Jay Flight with an Atwood 8525-IV furnace. The blower is continuously blowing even with the thermostat in the Off position. If I put it in the Heat position the furnace doesn't light but it has a single flash every 3 seconds. This is listed as "Limit Switch/Airflow problems". I have to use the switch on the furnace itself to turn the blower off.


Anyone have any ideas what would cause this? It was working fine a few weeks ago. Would a bad thermostat cause these issues? Thanks for any help.

[IamSpartacus]

Just had a similar furnace issue.

Troubleshot it down to 2 things - the sail switch or the thermostat.

It was the sail switch.

I just hope your furnace is easier to get to than mine!

[tcowen]

Thanks for the input. It's not very easy to access the furnace; only a foot or so of space so I'll probably have to pull it out to troubleshoot more. Is it very difficult to remove the furnace? I imagine removing the vent screen on the outside then I just see 2 screws holding it down in the front. Hopefully not any hidden screws.

[RichR]

If Jayco would put the outside furnace access door on the their trailers like other makes do, it would be much easier to check and service the furnace. It's all about saving a buck.

[tcowen]

Yes, that would be nice to have easier access.


I downloaded the Atwood Furnace Service Manual; lots of good info in there. The troubleshooting section for my symptoms says it could be either the thermostat or the control board. That makes sense to me as the motor relay is on the control board and my blower is running even with the thermostat set to the off position. The relay seems to be stuck closed.



I've ordered a replacement control board and also a rebuild kit for some of the other furnace parts. Figured I might as well replace as many parts as I could while I have it out since it's a 15 year old unit.

[pconroy]

Our sail switch was accessible from the outside. Hope yours is that simple too!

[MadGasser]

I work in furnaces for a living. Usually when the there's a limit switch fault you'll find air flow problems. In a residential application you'll likely find a dirty filter.

[tcowen]

Got a Dinosaur Electronics Fan50PlusPins control board and installed it yesterday. It fixed the problem. The hardest part was getting the exhaust vent removed from the outside; corrosion had locked it in a bit. Some banging, twisting and cussing did the job. I sanded it down before sliding it back in. I did have to drill out the standoffs from the new board to get it to attach to the bracket in the furnace. The furnace itself came out fairly easily; just 2 screws in the front and the propane line. The wiring was long enough to keep attached so I was able to test it after I replaced the board but before I slid it back into the small space. Overall a pretty easy repair. Thanks for all the input.

[JFlightRisk]

Thanks for following up with the solution, and the positive outcome. We appreciate it.