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Topic: Atwood Furnace 8535 III not ignigting (Read 774 times) previous topic - next topic

Atwood Furnace 8535 III not ignigting

Anybody have an idea on what might be the issue with the furnace in our 97, U295?  The furnace is an Atwood Mod 8535 III.  Last time we were out, I turned on the furnace but just got cold air blowing.  Today I tried to blow out the combustion chamber but nothing changed.  The fan will run, and outside, I could smell the propane. The igniter clicked 3 times, trying to ignite, but no go. 
Bruce & Jen Evans
Montgomery, TX
1997 U295 36'

Re: Atwood Furnace 8535 III not ignigting

Reply #1 –
OK, the fact that the propane valve opens means that you have adequate air flow.

The fact that the ignitior sparked 3 times and quit means that it was not able to create a flame that the thermocouple could detect.

Could be something as simple as a piece of rust shorting the ignitor or a mud dobber's nest preventing proper mixture.
Brett Wolfe
EX: 1993 U240
Moderator, ForeForum 2001-
Moderator Diesel RV Club 2002-
Moderator, FMCA Forum 2009-2020
Chairman FMCA Technical Advisory Committee 2011-2020

Re: Atwood Furnace 8535 III not ignigting

Reply #2 –
Reply #6 in link below may provide some guidance:

Random Questions on Heating

1993 U280 SE 40' WTBI, Build: 4359
C8.3 300hp, 6-Speed, Exhaust Brake
960 watts on the roof (6 x 160)
Sorento (or BOLT) on a Kar Kaddy SS
"Nature abhors a vacuum"

Re: Atwood Furnace 8535 III not ignigting

Reply #3 –
Ordered a new circuit board, and that didn't fix the problem.  The burner head screen was rusted through.  Ordered a new furnace burner head, and igniter just because I have it apart. 
Bruce & Jen Evans
Montgomery, TX
1997 U295 36'

Re: Atwood Furnace 8535 III not ignigting

Reply #4 –
Now might be the time to get a new fan motor,yours will go out sooner or later,like you say it's already apart.
96 U270 BUILD 4810
85 380SL
Drummonds TN.

Re: Atwood Furnace 8535 III not ignigting

Reply #5 –
Quote from: John44 –
Now might be the time to get a new fan motor,yours will go out sooner or later,like you say it's already apart.
He'll need a longish hex key to get at those lock nuts in the middle of the fan.
1992 Foretravel Grand Villa
U225 SBID Build No. 4134
1986 Rockwood Driftwood
1968 S.I.A.T.A. Spring
1962 Studebaker Lark
1986 Honda VF700C
1983 Honda VF750C
Charlie, the Dog was broken out of jail 24 Oct 2023
N1RPN
AA1OH (H)e who must be obeyed.

Re: Atwood Furnace 8535 III not ignigting

Reply #6 –
***UPDATE***

So, I started with the circuit board, which was the easiest part to access.  No change, so I pulled out the burner head, which was rusted, and since I was in there, replaced the igniter also.  Still no change.  Dug further and checked the sail switch and limit switch, and both showed good.  Still wasn't working.  Did a little more googling and found how to test the gas solenoids, and they also showed to be good.  I blew out the gas valve without activating the solenoids once and it fired up once, but wouldn't do it again.  Then, I activated each solenoid and blew out the valve each time, and put it all back together.  It is now working as it should.  It was a little time consuming but it was worth it. 

Thanks for the tips and suggestions. 
Bruce & Jen Evans
Montgomery, TX
1997 U295 36'

Re: Atwood Furnace 8535 III not ignigting

Reply #7 –
So, when you blew out the lines/gas valve, did you get an oily substance? Other?
Brett Wolfe
EX: 1993 U240
Moderator, ForeForum 2001-
Moderator Diesel RV Club 2002-
Moderator, FMCA Forum 2009-2020
Chairman FMCA Technical Advisory Committee 2011-2020

Re: Atwood Furnace 8535 III not ignigting

Reply #8 –
I didn't really see anything, but I think it was probably some small particle that may have blocked a passage way.  Nothing oily that I recall.
Bruce & Jen Evans
Montgomery, TX
1997 U295 36'

Re: Atwood Furnace 8535 III not ignigting

Reply #9 –
Way to hang in there.
1998 36 foot U270 Build No. 5328 WTFE, 900 watts solar, Victron controller, B2B, bat monitor, 600 AMPH lithium with 2018 Chevy Colorado toad, SKP #110239, Motorcade #17781, 2021 Escape 17B for when Coach is broken down and campsites are too small, retired and full-timer since Dec. 2020. Part of RV family since 1963.

Re: Atwood Furnace 8535 III not ignigting

Reply #10 –
Way to hang in there.
1998 36 foot U270 Build No. 5328 WTFE, 900 watts solar, Victron controller, B2B, bat monitor, 600 AMPH lithium with 2018 Chevy Colorado toad, SKP #110239, Motorcade #17781, 2021 Escape 17B for when Coach is broken down and campsites are too small, retired and full-timer since Dec. 2020. Part of RV family since 1963.

Re: Atwood Furnace 8535 III not ignigting

Reply #11 –
Quote from: Brucep86 –
I didn't really see anything, but I think it was probably some small particle that may have blocked a passage way.  Nothing oily that I recall.
Propane leaves a sticky, oily, residue.  The valves are gasketed caps that sit on the out flow stand pipes and are lifted off by electromagnets, and clamped back in place with gravity and light springs.  IF the problem returns it's either clean that area thoroughly or replace the valve.
Art
1992 Foretravel Grand Villa
U225 SBID Build No. 4134
1986 Rockwood Driftwood
1968 S.I.A.T.A. Spring
1962 Studebaker Lark
1986 Honda VF700C
1983 Honda VF750C
Charlie, the Dog was broken out of jail 24 Oct 2023
N1RPN
AA1OH (H)e who must be obeyed.