Replaced AC compressor, will not engage

Compressor on my SS locked up awhile ago.  Happened when I was topping up system after winter storage.  So, when I was working on it last fall, I swapped out the compressor for what I thought was a good used/rebuilt one.  Pulley free wheels fine, I can grab the clutch and turn over the compressor without issue.  Connector is plugged in.  I did new rear seals.

Vacuumed out the system (I have a pump and gauges).  It pulled down to negative 30 inches, and held for a few hours without moving.  Great, no leaks.  Time to fill.  Started car, turned on AC, connected a can and the vacuum pulled some in right away.  Compressor did not start.

Double checked fuses.  Disconnected the low pressure switch connector off the accumulator.  Jumped it.  Compressor does not start.  I do hear the engine increase slightly in RPM, so I'm sure the PCM is getting the AC on command.  I've never had one that DIDN'T start with the jumper wire.

Any ideas for me?  Am I missing something?  Or, is it just "take it apart again and throw another compressor in there"...

Re-reading Sprocket's threads, I wondered if I got the new type of self-sealing cans. Then I realized that wouldn't matter, the compressor would start by the jumper anyways.

AC relay?

Pulled it, re-seated. Didn't matter, I went back out, and checked for voltage at the AC connector. Full voltage when the car is on, AC on, pressure connector jumped. So, the car is telling the compressor to start. But it doesn't.

Sounds like the windings in the clutch have gone the way of Pontiac. Check for continuity across the windings. If memory serves, there is also a diode in this circuit. If that is open, then no power to the windings.

Bill

Maybe the clutch gap is too wide. It should be about the width of a business card folded in half.

Apply 12v to the compressor (eg: jumper the relay socket). Tap the front of the clutch. If the clutch will pull in and hold then the gap is too wide.