Atwood 8500 series furnace removal

roger66ogden · 07-07-2021, 08:00 AM

Hi All.
I have an Atwood 8500 series furnace in my 2001 320sr that the wasps have decided to build a nest in the combustion chamber.
Is there a post in the files section that covers the removal of the furnace? I don't want to disassemble half of the camper if it's not needed.

Thanks in advance
Roger

**JohnB** · 07-07-2021, 03:27 PM

Hi Roger,

I have had the 8500 totally apart before, just I did not do a post on just the furnace, but there is this one I did on my T1950 when I serviced it. That reply and the one following it show a lot of it apart.

https://www.sunlineclub.com/forums/f...y-17684-7.html

Here are the basics of getting the furnace out of the camper

Turn 12 volt power and gas off

1. Inside, unhook the ducts from the furnace. The round fitting must be removed to get the furnace out if the hole.

2. Then will be 2 or 3 screws inside by the ductwork that screws the furnace housing to the floor. Take them out.

3. Go outside, take white grate off, 4 screws in corners.

4. Pull the exhaust tube out, unscrew the wing nut and wiggle and pull the tube out. Un hook gas line on the left. Push the gas line through the red vinyl line seal. Hold the fitting on the gas valve while unloosing the tubing nut.

5. Take the screws out of the black plastic flange outside. Fold the metal tabs the screws were in, fold them straight out.

6 take a heat gun and warm the black plastic flange and using a dull putty knife and gently lift the plastic flange off the siding. Take care to not over flex it, it will break. The metal tabs will pull through the plastic flange.

7. Pull the furnace to the left and out about 1 to 2”. On the left side is a 4 wire harness that plugs into the furnace with a white connector. If you can unplug that white connector inside the camper, then do it there. Every floor plan is different if you can even get to that connector inside. If you can’t get to it, you may have to unwire it from outside then try and and get the white plug out then. The plug has to come out for furnace to come out of the camper hole.

Once your past wire connection, the furnace will pull out if the camper.

One word of advice, try and not separate the combustion chamber for the sheet metal housing if you absolutely do not have to. There is a white high heat gasket between the two that Dometic obsoleted. I have not found a source yet for that gasket short of making one yourself.

Hope this helps

John

roger66ogden · 07-07-2021, 05:14 PM

Hi John.
Thanks for all of the great information. Have you ever tried getting nests out through the exhaust pipe with something like a coat hanger?

**JohnB** · 07-07-2021, 08:19 PM

Hi Roger,

I have experienced bees/wasps nests before, they were real bad in the old farm house attic. That learning drove me early in the RV’ing life to install the stainless screens in the fridge, water heater and the furnace. And they have worked for me. Camco makes some to fit to your camper when you get out of this situation.

So no, I have not yet had a camper of my own or a friends I have helped with wasps or bees in the furnace. I had mud daubers in a pop up my some bought years ago, just not the furnace. And wasp nests in the roof AC to deal with.

This might help guide you. I’m not sure which variety you have, the wasps that make the round honeycomb nest that attaches on a real thin pedestal or the kind that make a giant paper machete kind of attachment and would plug the pipe solid.

The exhaust tube can be removed without pulling the furnace and the gas burner can come out as well. Then the entire combustion chamber inlet and exhaust ports are right in front of you. If you have a lighted flexible bore scope or camera you might be able to see deep into the combustion chamber. How to get the nest out, well maybe try using a shop vac as a blower and blow into the gas burner port, so air and crud blows out the exhaust. Then go in the exhaust port and try the wire dig it out trick. The blower will help force the loose stuff out back at you to try and not iget it in any further. I never tried that, consider it a thought to build on.

When done digging, go in with the inspection camera and see if you got it all. This much I will say, when the furnace runs, that side of the furnace gets real hot in that burner tube. I would think anything that is burnable left inside will burn. That is something to work through, make sure it is clear.

Any idea how big and bad the nests are?

Hope this helps and let us know how you make out.

John

roger66ogden · 07-08-2021, 11:44 AM

Hi John.
No idea how big the nest is. I tried firing up the furnace and I got crispy pieces of wasps that came out of the exhaust. Tried lighting it again and it didn't fire so I figured I'd leave it until I get the critters and their home out. I bought a screen as you mentioned and it was the wrong one of course but it fit my parents camper so that is as far as I got. Should have gotten the right one and put it on and I wouldn't be in the situation I am now lol