How do you know that the compressor is not seized?
It seems to me that there are two possibilities, since you say that the ac
pulley will not turn, no matter what you do.
You have not mentioned whether you have tried turning the ac
pulley with the ac
switched on and with the ac
switched off, and when the ac
pulley is locked up. All the time, or only when the ignition is switched on.
#1: The clutch pulley bearings failed, and the pulley was wobbling back and forth until it jammed itself against the ac
clutch coil real tight. This would explain why it will not turn. If this is what happened, then the compresssor itself might still be good, but you will need a complete ac
clutch assembly (magnetic plate, ac
clutch pulley, and ac
#2: The compressor itself has seized. If this happened while your friend owned the car, he would not have had to bypass the ac
clutch pulley to run the engine, as the ac
clutch pulley would have continued to work, and allowed the engine to run, as long as the ac
was not switched on.
Personally, I think that the #1 scenario makes more sense in your case.
If you don;t want to sink a lot of money into the car (what's a lot of money these days?). You might be best off, leaving the ac
If you are going to try to fix it, I would look for a inexpensive used compressor on eBay. You can usually find them for between $25-$40.
If money is a consideration, you should change over to R134a from R12.
Look for a complete used compressor assembly (compressor and clutch assembly). One from a later car that came with R134a from the Factory (must be from a 3.0L Vulcan engine. Then you should replace the receiver/drier, before evacuate the air from the system prior to refilling