Could anyone advise what could cause the AC compressor to "lock"? The engine would not start now, and it would seem the belt just rotates while the AC compressor pulley does not move.

Could this be the AC compressor needs to be replaced in it's entirety? I checked FastLane, but the compressor for my car is not listed.

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Turboman

1993 300CE Garnet Red
Eibach Springs
18x8.5 ADR M-Sport wheels (Hyper Silver)
Metal Master brake pads
Semi-gloss black front grill insert

Yep, that's what it could mean alright. Replacing the compressor is not the worst of it. After internal compressor failure it is MANDATORY that the ENTIRE SYSTEM be THOROUGHLY flushed EVERYWHERE. There is lots and lots of debris in the system that, if not removed, will destroy your new compressor in short order.

To preliminarily check this, with the engine off, try to rotate the very forward part of the clutch mechanism. If it will not turn at all, then the compressor has failed internally. If it turns by hand, then you are very lucky and this means that the clutch is the problem.

Good luck,