[Chester Stone]

Richard, I will do what you suggest and check the voltage with the compressors running in their original configuration and with the leads switched.

After thinking about this issue over night, I decided to check the voltage output at the thermostat to the board under high and low settings. Then I will check to verify that the output from the therm is being received at the pins on the board. I think these should all be 12v readings. It seems to me that this should be easy to do and should tell me if there is a problem with the therm or wiring to the board. I will also verify that 12v power is coming into the compressor 1 section of the board. I should have thought of these checks before, but with your help I am learning as I go.

In an earlier post I pointed out that when the therm is on high, the amp draw by compressor 2 is about 8 amps with compressor one drawing 4 amps. Recently, with the therm set on high, I disconnected the wires to compressor 2, and compressor one drew no amps. Strange. This led me to question the output from the thermostat. The above voltage test should also be interesting.