Attwood 8535- no ignite- cannot get exhaust out

[Dale70]

I am diagnosing an 8535-IV with single sense electrode.
Circuit board was not tuning on gas valve
Replaced board -- now have valve turning on -- but no ignite

want to remove gas valve since large mud dauber nest was in that area.

Problem is I cannot get exhaust to slide out -- even with wingnut loose.

Before i put a lot more pressure on it -- I would like to know if that exhaust is a smooth fit where I might twist it -- or it is slotted/indexed or anything else????

Unit is on the bench to I have decent access.

thx Dale

[Skidaver]

Check out the exploded view in the link below for the answer to your question. The exhaust tube or "draft cap assembly" as they call it, slides straight out.

https://dunesport.com/manuals/atwood-furnace.pdf

I had mud dauber nests in my exhaust tube and in the heat exchanger, so I know what you are up against. Good luck.

[Dale70]

I am hoping it is that simple --- have some penetrant soaking tonight.
My unit does not really look like that, since those photo's cover a lot of units.

We will see

thx Dale

[Skidaver]

Are you getting any airflow out of the exhaust? I haven't explored the sail switch's function, but it may be preventing ignition if there isn't sufficient airflow. Just a thought...

[Dale70]

I did not get the exhaust out --very rusted -- but got the larger oversize piece off of exhaust so gas valve could clear. Will have to deal with refitting that somehow.

The gas valve is working, sail switch working, limit switch working, but the burner had a lot of holes clogged with redish material.

I ordered a rebuild KIT --- about $50 ---which has new sail switch, limit switch, single wire sensor ignitor, gas valve orifice and new burner. Plan to put all those in as unit is 18 year old.

Let you know results when I finish.

thx Dale

[Dale70]

Just to wrap this up -- the furnace seems to be working fine now -- although I have just tested it here at home several times.

I had ordered the kit with burner, ignitor, sail switch and limit switch.
I put in the new burner and ignitor. reinstalled the furnace, and it started right up on the first try. I cycled it several times and it seems ok.

I then replaced the new board I had purchased with the old one. It worked fine on that board, so it was not a board problem. The new board did however help me find the problem as it has an LED which flashes and give a cause. That helped me decide it was either the burner or ignitor.

I put the new board back and will keep the old board, sail switch and limit switch as spares which will fit both of my furnaces, as they are both the same 8535-IV model

thx Dale