Atwood Furnace 8535 IV, Repair tip.
This is the only Atwood I've messed with, so not sure how much might apply to your furnace.
Symptom. A light popping sound while fired up. Not explosive sound but enough to tell me its not working like it should.
I felt it was somewhere in the gas feed post control valve cause it was firing and heating. But I didn't catch that it might not have been at full heat.
Two possible issues found, one was most likely the cause.
1. The furnace burner (a screened diffuser, flame spreader) looked a bit rough, some scale, rust and a stink bug was inside the furnace burner. It might have messed up the flow a bit.
2. I removed the orifice and found a couple pieces of debris behind the orifice. It was not blocked or totally clogged. It looked like the debris might have been tumbling around, again messing up the flow a bit.
I replaced the furnace burner and cleaned out the orifice and checked the valve to orifice tube for any other debris. The debris almost looked like drier lint, but real small.
The heater is now back to roasty toasty.
A maintenance suggestion.
The only slight road bump is removing the exhaust pipe. You have to remove it to get the gas valve out. Its only retained by a wing nut and it slides into the heat exchanger by maybe 2-3" give or take. The exhaust pipe was rusted and stuck. A bit of PBR Blaster, some careful wiggling up/down left/right and it finally came out. It did take some time, trials and not getting heavy handed. The suggestion is to consider removing the exhaust pipe yearly, put a light coat of anti seize on the section that slides into the heat exchanger. This might make it a bunch easier to remove the exhaust pipe for any servicing of the gas valve, etc.
2005 Dodge Ram 2500 5.9L 6 Speed
16" Michelins, Hi Spec Wheels, Max Brake, Carslile Actuator, Equal-i-zer, Dill TPMS. Campfire cook.