Atwood Furnace Behaving Strangely

[TheRogues]

I have a 2000 Fleetwood Southwind with two Atwood 8520-IV furnaces. The rear furnace is lighting and shutting off continually, and not stopping after three tries. Turning off the thermostat does not stop it. I have to use the master switch on the unit itself. My thermostat is the intellitec non-digital type. I have tried switching the circuit boards with the front unit and no change. Front furnace works fine. Every once in a while it will function properly, but hardly ever. Right now it’s not usable. The burner was recently changed and I’ve made sure the electrode and sensor are clean. Not sure how to proceed from here. Anyone have any thoughts? Thanks.

[Jon_C]

Swap the control boards and see if it follows or not.

I have seen low gas pressure cause that also. Make sure the line is not kinked


Edit: ok i see now you already swapped boards..

[MrMark52]

Just had a somewhat similar situation with our ‘02 Atwood - a few weeks ago, it came on and sputtered for about 10 seconds then died.
No breakers tripped, no fuses blown.

Today I dug into it - after finding weird and fluctuating input voltage readings and taking the whole unit apart (needed to lube the motor bearings anyway) - I found that where the the input power wiring was wire nutted to the input power connection for the furnace appeared to have slightly melted. I took the connection apart and found it was poorly made from the factory.
Remade the connection, furnace runs great now.

Moral of the story - if you’ve checked the spark gap and swapped circuit boards - start looking for possibly intermittent wiring, loose connections, corroded or failing grounds, tight thermostat connections - and last but not least, wiring damage caused by mice and rats.

[TheRogues]

Do you know the link for the proper gap information? Thanks.

[Old-Biscuit]

Originally Posted by TheRogues

Do you know the link for the proper gap information? Thanks.

Atwood furnace spark electrode gap ----- 1/8"

Furnace not shutting down is due to BAD 'Time Delay Relay'

**Newer Versions incorporated TDR onto the Circuit Board
PWR connection and BLW connections

[TheRogues]

Forgive my ignorance, but is the 1/8th gap the distance between the electrode and the sensor wire next to it, or the distance from the surface of the burner? Thanks.

[Old-Biscuit]

Originally Posted by TheRogues

Forgive my ignorance, but is the 1/8th gap the distance between the electrode and the sensor wire next to it, or the distance from the surface of the burner? Thanks.