Heater Delayed ignition problem

[davidspixx]

I have a 2015 Vegas 25.2. The Atwood (now Dometic) furnace just started a problem called delayed ignition. It is when the furnace on startup delays before the propane is lit, resulting in a roar or a boom that lasts maybe 10 seconds. It is normal after that.
With the propane off, I disassembled the propane fire part (SIC) with the spark ignition. The unit was very pristine, no soot, etc. I regapped the spark unit. Turning it on, I verified the spark unit working properly. Reassembling the unit it still had the problem. I also checked for blocked airflow in the inside, but flow from the heater blower was strong.
I called Dometic for customer support but was told that they not have a consumer technical support department, and that I should contact CW. Does anyone else have this problem, or know where I can get support??
Thanks
David

[javelin]

After a little exploratory web cruising it could be many things.... from too much air making the gas mix hard to ignite; wasp (mud dauber) nests apparently per attached hyperlink; and also too much gas pressure from the regulator perhaps; faulty electronic ignition etc. Sounds like it is not good to allow it to continue as you might imagine......damage to the furnace is very possible. You might want to get some expert tech involved ASAP if you were unable to see anything obvious.


RV.Net Open Roads Forum: Tech Issues: "explosive" sound when furnace ignites--SOLVED

[mtntrek]

Sounds as if you've covered the owner's stuff.
Guessing that you verified the burners draft fan is not obstructed. Much like an internal combustion engine the proper fuel / air mixture is required for timely ignition. Perhaps there is and issue with the gas valve? There is often an ignition solenoid, then after flame proving, the main burner valve opens. A tech may be able to attach a manometer to test ports to verify fuel delivery pressures during those phases.

No change in fuel quality recently? Sometimes the main LPG regulator(s) can fail also. Other gas appliances operating properly?
Best of luck.

[davidspixx]

Thanks guys.
Yes I figured that it was due to a lean mixture. If it continues or is dangerous (IE not a "poof" but a bang, I'll probably replace the gas valve sub-assembly.
But again thanks.
David

[davidspixx]

I first followed the tact of my mechanics, I replaced the electronics card. (I had a spare) - no effect.. I replaced the burner assy (new from ebay $50). Questionable benefit.
I hired a friend RV mechanic. He blew out the burner side of the furnace with compressed air (much dust came out), he re-gapped the spark and the gap from spark to burner assy. (both were way too close). He verified propane pressure and that it did not drop when fridge came on. He leak tested the connections.
I will get back on this if the problem resumes. I am hopeful.
David

[axis earl]

Originally Posted by davidspixx

I first followed the tact of my mechanics, I replaced the electronics card. (I had a spare) - no effect.. I replaced the burner assy (new from ebay $50). Questionable benefit.
I hired a friend RV mechanic. He blew out the burner side of the furnace with compressed air (much dust came out), he re-gapped the spark and the gap from spark to burner assy. (both were way too close). He verified propane pressure and that it did not drop when fridge came on. He leak tested the connections.
I will get back on this if the problem resumes. I am hopeful.
David

Found out that the Atwood furnace heater on our Axis started doing the same thing. The longest that it stayed lit was about 10 seconds and would never stay lit. I was on the road and had a local mobile RV repair person look at it who said that the circuit board was bad. Of course, he was not able to prove this to me since he had no replacement and I wasted $250. Lesson learned. I will be taking it to my local RV service place and let you know what the problem is. All other gas appliances, i.e., refrig, stove and oven work fine.

[axis earl]

The problem with the Atwood furnace heater not lighting off was apparently the circuit board, just like the mobile RV repair guy said.