Atwood water heater issue.

[Steve079]

Bought our Springdale 179QBWE in 2017. The refer was replaced under warranty right after purchase, but since the replacement, everything has worked great, until this past weekend.
No hookups at our site, fired up the hot water heater, and went for a walk. Came back to smell that dirty propane burn; the back vent showed soot and it had gone up the side about a foot. Water was hot, but never came back on the rest of the trip.
Since returning home, I have blown out the burner tube and flue tube, ran a brush down the flue tube from the top and bottom, The tube still looks black with soot, but no blockage. Both the 2amp fuse on the circuit board, and the thermal cut off fuse look good. I've tried turning off the valves at the tank, remove/reconnect the hose, and slowly open the valve.
I have not pulled the electrical connector clip off the board, or removed &cleaned the gas orifice ( jet?). The electric side still works. The Atwood switch has a switch for both components, and a red light in between. It didn't come on when the unit failed to light, and I don't remember seeing it on when the water heater was operating.
I don't know what to check next? Its a gas/electric combo 6 g.

[chuckster57]

Remove the burner tube and inspect for spider web(s) at the burner end. Compressed air doesn’t always clear them.

Does it try to light? Any sparking at the igniter?

[Steve079]

First I blew it out while camping, then yesterday removed the tube completely, nothing but the screw that secures the adjustment sleeve in there. There was a metal shaving stuck in the flue tube, probably there since the unit was assembled. I cleaned the flue tube as outlined in the Atwood manual, then blew it out again, reassembled it. No gas smell, no clicking at the lighter.

The heater worked when first it was switched on, but once it shutdown, it didn't restart, and that's when I noticed the smell, and then the soot.

[chuckster57]

Ok. So now you need to test for voltage at the gas valve. All that soot is indicative of a “lazy flame” and it may have overheated the control board.

We use a 12V test light. You need to verify 12V going into the board, back probe or remove the connector. DO NOT attempt to test the igniter connection as it is high voltage and will cook your test light.

Use the test light to verify the fuse is good on the board or an ohm meter. I’m leaning towards a failed board.

[Steve079]

I did check that fuse, but only visually, but it looked good. I'll check out the voltage, thanks.

[Steve079]

One of the two brown wires has a fuse inline, though it looks OK, no voltage is going thru, Guessing thats the culprit?

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[chuckster57]

Coming from the board to the “ thermostat”? Bypass it to test.

[Steve079]

Thought about that, wasn't sure if that was a good idea or not, I'll give it a try right now, thanks...

[Steve079]

That was it. Fired right up. Too bright out to see the pilot color, flame going up the flue tube looks orange, guess I'll wait until sunset.

[Steve079]

Learned a lot today. Got some help from Chuckster57, and figured out the problem was the Thermal cut out fuse between the Tstat and circuit board. Watched a couple videos about using a multi meter, (which I've only ever used as a volt meter) Found the parts I needed on line, from Atwater, and should have things buttoned up and ready for the next trip in a couple days, I'll be more prepared for this issue, should it happen again, and will have the spare parts on hand to fix it.

Thanks again Chuckster57!