Troubleshooting remotely, so bare with me.

Father-in-laws compressor seized, smoked and melted the drivebelt.  he is wondering whether he can run the car without that drivebelt.

 

there are 3 pulleys on that belt: AC, Crank, and something I don't know.

Is the lower one just an idler or is that important?

 

Thanks.

The lower one is the belt tensioner. Make sure it was the compressor that actually seized and not the tensioner pulley.

Just spin it and see that it moves freely?

Compressor clutch has to be engaged for the pulley to drive the compressor. If the AC is off the outer pulley should spin easily.

Normally you should be able to rotate the center hub of the compressor (that part with the three straps on the front) by hand easily. If the hub can't be turned by hand, then yes, compressor is locked up. You can leave that belt off entirely and it won't affect anything.

 

Do check the lower idler pulley. Much more likely for that to seize, and it's a lot cheaper than a compressor.

I assumed last week that it was the compressor and pulled the relay.  I will check the tensioner.  Thanks

The idler spun freely, but I could hear it.  I tried to spin the compressor pulley and could not by hand.

 

Or did I screw it up by not spinning the front part?

If you can't spin the outer part, the pulley bearing may be locked up or something in the clutch could have jammed.

Try spinning the hub, if you can spin that by hand the compressor may be OK internally.

You can remove the pulley with a special puller and see if the bearing locked up or if there is something jammed in there, but if the pulley locked up there's a good chance it has overheated the compressor and caused it to grenade inside.