Water heater problem

[awellis3]

The Atwood water heater on my new-to-me '95 Sunline won't cycle off when using shore power. (Model GC6AA-7 - ser.#96152022612)
Here's the deal - Hook up to water spigot - open spigot to fill lines - open both faucets at each fixture to bleed lines - shut off spigot - open faucets at sink to relieve pressure, then close - open safety blow out valve at WH to create air pocket - close valve and cut spigot back on - turn on power to WH. In about an hour the safety valve opens and boiling water spews out.
Turn off power and light gas pilot. Gas valve opens and WH is off and running on propane. The WH comes up to about 165 degrees and the gas cycles off.
What's the problem? AC power control? Tank sensor?
Much obliged,
Teach

[Steve Collins]

Sounds like a bad thermostat to me.

The 110 vac part of that water heater is totally separate from the 12vdc/propane section. On the back of the heater, you will find a switch, the main 110vac line, a thermostat and a high temp limit sensor. The last two are physically connected to the tank itself.

This is the backside of the heater. Mine has electronic ignition instead of manual pilot, but otherwise should be identical to yours.

In the center of the heater, there is an aluminum box. You can see the white 110vac wire entering from above. On the top side of that box, just to the left of where the blue wire connector is, you will find a rocker switch that turns the heater off and on. At least there is one on mine. In the lower right corner of the box you can see a hol and a red button. That is the high temp reset switch. If the heater goes over temp, that trips like a circuit breaker and has to be pressed to reset.

If you remove the rectangular cover and trace the wiring, you will find the thermostat.

[awellis3]

Boy, your stuff is always so tidy. The back of my WH looks as if a pack of rats tore the thing up. I'll try to squeeze my fat a$$ under the bed and get to all this stuff.

Thanks mucho,
Teach