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Pol6 · 07-08-2016, 06:14 AM

Hello, I'm new to this site and RV'ing. Got me a 2012 class A motorhome fitted with a 10 gal Atwood electric/gas water heater. The unit was working fine until recently when the electronic module and wiring insulator melted down on the brown wires leading to the thermostat. My first call was that it was caused by a defective module that shorted. Got me a new module and thermostat and melt fuse. I started the unit on gas and it ran except for the fact that it was generating a lot of heat to a point where the cover was extremely hot, So I checked for clogging in the burner tube by passing an electrician wire pull that came thru without any residue. Reajusted the flame to 1/4'' opening and reignited the heater. It seemed Ok and I was checking on and off and after about 10 minutes, Meltdown again...! Never found any post about this type of problem on the web. I'm pretty good fixing electrical and mechanical stuff but this dazzles me.

okcnewbie · 07-08-2016, 07:02 AM

This sounds serious....be careful.

With the new board does the unit work on Electric only (AC)?
I'm not sure if you're saying it melts because it's getting too hot or because of too much current through the wires. These are typically fairly simple devices but perhaps yours has new tech built in?

Pol6 · 07-10-2016, 04:53 PM

The problem is not electrical, there is simply too much heat built-up behind the panel. The electric heater is still working and even the gas side will still light up even tough the control module is a bit out of shape. I'm not using the gas anymore until i find the cause. It's way too dangerous ! I was thinking that the melt fuse on the brown thermostat wire would protect the unit from this type of malfunction.
My guess is that the burner tube does not exhaust adequatly wven after passing the wire pull thru it. I will head head to my RV dealer service dept

phays · 07-10-2016, 05:49 PM

Check to see if the flue on the water heater is clear. You can remove the baffle at the upper left corner, the burner assemble at the bottom right and push a flexible rod through the flue. Or, as an Atwood tech said at a seminar, drop a golf ball in the top of the flue and if it doesn't come out then the flue needs cleaning.

While the burner assembly is out it is easy to check the burner tube since you now have it in your hands. Usually a restricted burner tube will allow flame to come out of the burner tube vent holes near the orifice which would cause this problem.

Pol6 · 07-10-2016, 06:49 PM

Thank you Pete,
There is no way a golf ball will get down the flue. It is round at the bottom but at the upper elbow I can see that the tube is sort of bent inwards as to create a permanent restriction within the tube. Looks to me as this is factory made cause it's well centered and symetrical.

Pol6 · 07-21-2016, 12:15 PM

Finally I had to install a new heater. The flue near the exit was 'crushed' inwards and created restriction that caused the hot gases to stain within the unit where the controler board is. Found this after the third meltdown... We think that the unit froze and the flue tube was the weaker than the tank itself. it still does not make sense to me but there's no other explanation.
I'm done with cold showers ! Yeah..!