Why Is My Heater Thermostat Working Backwards?

[mrwrick]

Help! My heater thermostat is showing voltage, 120, when it is in the OFF position. When it is turned UP it shows no voltage to the heater plug. I have tried switching pairs of wires on the T-stat and also on the heater relay rectifier, with same result. T-stat is new, checks out OK with continuity. Relay is new, operates when it gets voltage. Heater is not the problem, it has 9.8ohms and is just waiting for voltage. The T-stat wiring conversion from DC to AC has been done. What can be checked, what re wiring is needed, what unit is suspect? I am about to go test the rectifier. This is in a 1993 Hot Spring Classic F. A lot of great help here has gotten me to this point. I just need to get this heater going and will be done. Thanks

[PreservedSwine]

Where, EXACTLY, are you measuring voltage? The thermostat should have 120v on one side until you close the circuit, at which point the 120v travels through both leads on the way to the rectifier.

Posting a clear picture of your control box wiring will help as well.

[mrwrick]

I was measuring voltage at the heater plug outlet in the control box. I tried putting the old relay back in to see what the result would be. Initially I got voltage, 119, when thermostat was turned up. But when I had it all put back in the thermostat clicked, as if turning heater on, but since then nothing. The new relay I had put in is a double pole, double throw unit. Now I suspect that may be the wrong type. It has two more terminals than the old relay. Thanks for keeping up on my problem, PS. Chad