No power to gas water heater switch

144Grayling wrote:
Thanks for all the replies. It is a suburban SW6D. I got the service manual on line and it said to check the voltage across the switch terminals so that is what I did. (Meter in parallel with switch) Zero voltage. The manual says if no voltage to check the 12 volt power input to the switch but I’m not sure how to do that. If it were a car I’d just go to ground. Does that work on a trailer? I can unplug the wires and try that way but there is almost no slack in the wires and I’m afraid of losing them in the wall. There is no fuse in the control center for water heater. The switch is mounted to the wall so I have no idea where the wires come from or go to. The service manual schematic shows a positive wire coming into the switch and a wire out the other side to a junction box but I have no idea where those are in the trailer itself. Where could this circuit get its power if not from the control center? (Note there is also no fuse in the control center for the LP detector and it’s not getting 12 volts either.)

Weird. When I went to check on it this morning it was working! When before the red light did not come on at all, it did this morning, then of course it goes out when it starts. So I might have an intermittent failure situation.
Again any suggestions would be appreciated.

Very similar to a car test. Keep the black lead on ground and use the red lead to verify presence of 12v at the switch. Both tabs with switch on. Then use the red lead to check the two thermodiscs located under the black foam cover. There are two in series. One is the thermostat that sets water temp, and the other it the "over temp" safety thermodisc. If you have the black lead grounded, you should get 12v at all four of the disc connectors. If you lose it, one of the discs is bad. This is, of course, when you have cold water and the heater is calling for heat.