My 1984 300TD has two ice cube relays on driver's side fenderwell. One controls the compressor clutch, the other the aux fan.
Does the compressor relay switch positive or ground?
The only way to get the aux fan on is to jumper it at the receiver-dryer. The only way to get the compressor on for a test is to jumper two relay pins. It works but is not getting a signal from the ccu unit in the dash.
Is that signal positive or negative?

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Stage Wizards Lighting and sound designer
1981 SD 328,000
1985 300TD, 266,000
1984 300 TD, 267,000