A/c system stopped blowing cold air, recharged and cold air returned for a week or so, traced leak to compressor after adding dye, found dye around compressor clutch assumed shaft leaking. Intended to rebuild compressor (10PA17C) but found a rebuild on Ebay for $175.00. replaced compressor, receiver dryer added oil per MB manual, held vacuum at @30in for 1/2 hour. Began adding freon, jumped switch to activate compressor/clutch and nothing happened. I compared the ohm readings at the three pins between the old compressor and new, finding pins 1-2 = @825 ohm on old compressor but open on replacement, I am assuming this is the coil, cannot locate a drawing to confirm. During t/shooting read many stories about relays and control modules, and I had power at fuse 7 and at wire to pressure switch, but never at the compressor, my big question is do I need a working coil to get power at the compressor? or did I set off a cut off switch or something by putting in a crappy compressor? Yeah I know should of checked coil before install.

Pins # 1 & 2 measure the speed sensor, & pin 3 is the compressor clutch coil.

Measure resistance between # 3 & ground to check the clutch.

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thanks for the info I'll check that when I get to work on the car Thursday. Do you know if I can remove a relay and jump the pins? I have read where the compressor relay is same for fuel pump so car wont run with relay removed. Thanks again