my atwood 8531 III furnace is having issues last year the fan would run but it would not ignite i checked voltage from sail switch and that was fine there was voltage to gas valve
took board in and it checked out good. put board back in this summer and furnace ran fine
last week furnace ran for the day and at night it would not fire.next day it ran for the day
and not later that eve. following day it would not run at all. I can here the gas valve
click the 3 times and smell gas then it will lock out. what else can i check and how do you get to ignitor as the gas valve is blocking access to it. can there be dirt or bugs inside exhaust tube. there was a lot of wasps in the furnace last fall
Yes, Wasp's can built nest inside. You can try using an Air hose to blow the Flue out but, those dare Mud Daubers built rock hard nest.
What I had to do was remove Heater and stand up the heater. Then filled the chamber with water to soak over night. Rinse and repeated several times.
Adding some Ice Cubes may help to dislodge the nest too.
PS- it's a little late but, maybe add a Outer Screen to keep the Insects out after you get it fixed. The Screens are available at most RV Parts Stores. But , well worth it.
99 Fleetwood Vision 36Zulu V10 Gas F53 Chassis
Hyd Leveling man/keypad (Powergear)
Electric Slideouts (Powergear) x2
2005' 4020 Fadal 4Axis CNC Mill w/24Datc
Hendy 16x72" WWII Navy Lathe 1800RPM
I too have an Atwood 8500 series IV furnace in my 2003 Southwind. I just had a VERY similar problem this weekend camping in the CA redwoods. Worked one night fine but not the next. Essentially I had intermittent operation with eventual fan shut down. The red LED (on the ckt board) flashed 2x then off 3 seconds, to indicate ignition failure.
I took the board in to get checked at a local repair shop. The tech told me even if the board checks good, it can still be bad, especially the Atwood factory boards. He suggested I check continuity and voltage to the board from the sail switch/hi limit switch before spending $170 for the board. Took it back and reinstalled the board. Did the tests which all checked good. I even took the housing off the fan to get to the sail switch to see if dust was fouling it up. When I put it all back together, the symptoms changed to airflow failure (LED flashes 1x, 3 seconds off). I called the shop and he said it must be the board.
Bought and installed the new (Dinosaur Fan 50 Plus Pins universal replacement) board, no ignition...RRRRGGH! While testing the voltage at the terminal block, the light went green and the ignition fired. Turns out, the blue wire from the sail/hi limit switch circuit wasn't making good contact at the circuit board. The pin that goes into the terminal block (connected to the wire) was flattened and not making good contact. Poking in there with a voltage tester gave it momentary contact. Anyway, I took back the board and bought a dental pick set from the local Ace Hardware. Bent all the contact points up to ensure good contact. Reinstalled the old board and it fired right up. Good thing too since it is in the mid 30's tonight. My electric heater won't maintain temp when it's below 45 outside.
I was fortunate the repair shop took back the circuit board. They usually don't allow this with electrical parts. Mike and Tim were a great help. (R V Services Center of Santa Cruz, 2525 Mission Street, Santa Cruz, CA 95060, (831) 427-0881)
BTW, this makes the third bad connection I've found on my motor homes. Slide out ckt board (bad solder joint) & water heater spade connector were others. My new thumb rule is, if it looks relatively new, it's probably not bad. Check the connections first.