Atwood 8535 III furnace problem?

[Bubba_Bill]

'95 Damon Intruder. Furnace just quit working, blower ran, no ignition. Motor replaced last year, worked 2 months through Winter O.K. Tested O.K October. Replaced sail switch with 'replacement no.' switch, but paddle slightly smaller. Replaced board with Dinosaur board (figured it was due!), still: blower runs, no ignition, tries to ignite, shuts off, repeats. Open outside door: starts right up! I can close outside door(s) and runs happily. I checked just about everything for mud daubers, nests...you name it. Blew out chamber with compressed air. I'm about to try adding a piece of alum tape to increase size of sail switch paddle. Any ideas Guys? Bill

[lasttruck]

What fault code do you get from the light on the circuit board?

If the ignitor has a strong, consistent, steady spark (weak may sound ok, but there is a difference). Had that problem on my smaller RV. The ignitor tips may appear fine, but the resistance is within.

On the PM, the 8940's blower wheel tossed blades twice. Apparently struck the limit switch one time. Sometimes the furnace would run, sometimes not requiring a reset. Replaced the limit switch (relatively inexpensive) and no more problems.

[jergeod]

Try using a wire through the chamber some of the spider nests are attached so well that air is not going to remove them. (those white fuzzy ones) Just a guess.