Quote:
Originally Posted by MarkEHansen
The two blue wires (thermostat) will have 12V on one and nothing on the other, until the thermostat calls for heat. The 12V comes from the furnace on one of the wires and goes to the thermostat. When the thermostat calls for heat, it will basically connect the outgoing wire to the incoming one, sending 12V back to the furnace on the second wire.
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Ya... the thermostat was calling for heat, you could hear a single relay click from the furnace compartment when the heat was 'turned on," and another when it was "turned off." We had it "turned on" while he was testing voltages.
I doubt the problem is the furnace gas valve. That failure shouldn't even show up until after the fan starts and the sail switch affirms, and the fan never even tries to start. (Hm... maybe the problem is a bad fan or bad fan wiring.)