I expect that this car still has an old York style 2 cyl. compressor. These critters just won't hold up to the additional pressure of 134. Been there, done that. I have reverse converted one and replaced the compressor after totally and thoroughly flushed the system, changed r/d, added mineral oil, evacuated and charged.

The good news here is that these compressors are cheap.

Without the engine running, start by jumping 12 volts directly to the clutch and see if it clicks. Without voltage applied turn the compressor by hand and see if it is free. If you are successful with both of these, start tracing the clutch circuit and don't overlook checking the fuse.

Good luck,