Hello. I'm having problems with turning my a.c. and furnace on. I have a rear thermostat that runs the furnace and rear ac. I have a front thermostat that runs the front a.c. and it's working fine. I have a 1994 thor residency motorhome. It has an analog dometic duo therm thermostat. Atwood furnace 8940dclp. The ac is a dometic but not positive model number right now. Originally my rear thermostat stopped working. Lights wouldn't come on or function at all. I replaced with the same exact model. Now I can toggle through all the light settings but it still doesn't power up a.c. or furnace. I've checked breakers and fuses in the breaker box and all are good. I was able to jump the wires at the furnace and it runs fine. I was not able to jump wires at the thermostat for furnace but not positive if I was doing it right or if possible. Could use any test or tips because I'm at a dead end on what to do.
A/c and furnace won't work
- Thread starter Padtrx
- Start date
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Gary RV_Wizard
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The thermostat merely sends a "heat needed' or "cooling needed" signal, which in an RV is done by placing +12v on a wire that runs to the appropriate place. Sounds like that new thermostat isn't doing that. It needs 12v input, so check for power (fuse?) on that wire. The thermostat basically just connects that 12v input to the heat/cool needed wires when the set temperature is exceeded. You should be able to short the 12v input to the output side and cause furnace or a/c to run.
I have 12v coming from the red wire in the wall. There is also 12v coming from Brown wire in wall. There's nothing in other brown wire and ground coming from white wire. Then there is the ribbon wire for the ac. The red 12v wire lights up the thermostat. I tried putting the two brown wires together to bypass thermostat for furnace but got nothing. I was able to only jump the furnace at the furnace. I opened the ac up and there is power in the conduit line running to board. Fuses in breaker box all tested good with a test light. Is there fuses or breakers hidden somewhere else I should be looking for?
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