Community Forums

bigben · 12-05-2017, 05:48 AM

Note: This was also posted over at Thor Forums but thought I update my post here as well. Hopefully it will help someone else out.

I need to followup on the original post found here: Furnace won't light - simple fix

We normally use our electric heaters while we are traveling in the winter but due to a family illness -we have had to go back to the land of the cold in Kentucky. Weather forecast is horribly cold for this week (mid teens) and I fired up the furnace to make sure we were ready. What I found was NO FIRE in the furnace = no heat for the basement. Fortunately we had a couple of days before the cold set in.

Symptoms again:

1. Fan started up.
2. Slight smell of propane.
3. Ignitor was heard sparking.
4. No ignition
5. Furnace attempted to start 3 times.
6. After 3 failed attempts the control board began the 3 blinks, 1 second, 3 blinks coding indicating a soft lockout.
7. After about 30 minutes furnace soft lockout cleared and sequence above was repeated.
8. Using the reset button on the furnace, this sequence can be bypassed and the soft lockout is reset.

After reading a great deal from several sites (as I'd already done), I decided it was either a clogged burner or the controller board. Got hold of Atwood customer service and they indicated that these two issues sounded correct. The emailed me the specific manual. I found the controller board on line but decided to try and clear a clog.

I opened up the furnace on the outside of the coach, shut off the propane, removed the propane lines, fired up our stand alone compressor, reset the furnace, waited for the ignitor click and then started blow air into the furnace propane regulator. I did this for each of the three cyles, hit the reset again and then blew more compressed air into the regulator.

I then reconnected the lines, hit the reset button and ShaZZam - igniting. I let the furnace run some more, shut it down and then had it start back up. I still had the love - furnace is working great, ready as we can be for the fierce cold.

Here is the specific manual for the AFMD 35141 Atwood Furnace and pic of the spot that I used to blow out the blockage:

wa8yxm · 12-05-2017, 06:16 AM

Another common issue with DSI Furnaces (I have only worked on TWO DSI furnaces and the BOTH had this issue, My Propane job and my parent's oil filred, so for me it'a 100% common) is excessive ignition gap. If te spark (Roughly 1KV ac) can not jump the gap.. Well it won't ignight.

Reset PER The manual and operation (in both cases) was 100%

tcopeland · 12-06-2017, 10:30 AM

An issue I had: neither of my furnace compartment outside covers were sealed in any way. During a heavy rain water shorted out both control boards. Thor sent two boards free of charge and I replaced as a diy. Installed a rubber seal around each panel. No issues since.
Something you might check.

Old-Biscuit · 12-06-2017, 10:50 AM

You LUCKED OUT....BIG TIME

Propane system uses 0.4 psi
Should never induce air pressures over 0.5 psi thru gas valve

High air pressures can destroy the Main orifice and/or the gas valve

Your 'simple fix' could have ended up being very costly.....replacement of gas valve and orifice

This is NOT a proper method for 'repair' and should be avoided

More then likely the main orifice was clogged and should have been removed, soaked in alcohol and then blow thru it by mouth (or VERY low air pressure)