Don't worry about the refrigeration untill you can get it to stay on.

The compressor is controlled by the Klima relay and the V8 doesn't use a speed sensor on the compressor. As such about the only thing that should make the Klima ignore your "on" command would be a wrong temp reading.

I usually pull the Klima and jump the output to make the compressor run. With the Klima out the other inputs to it are available for testing. Get your wiring diagram.

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Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician