Good, then it is an R4 compressor. I replaced mine years ago with a Four seasons rebuild, only $97. If the compressor is good, you should be able to turn that triangular plate by hand. But before you change the clutch, check the resistance across the 2 clutch terminals. Should be a bit less than 1 ohm I think. If it IS that, test it again by jumping it direct from the battery (briefly). Reason is, that clutch takes a lot of current, and just because you have 12 volts doesn't mean you have 15 amps or so going through it.

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'82 300SD - 361K mi - "Blue"

"Good judgement comes from experience. Experience comes from bad judgement."

listen, look, .........and duck.