Serpentine belt squeal issue A/C compressor

[GMC87]

So my serpentine has been squealing on my 87 (454). After replacing the belt checking the tensioner I found out today that it is actually the A/C compressor pulley will lock up when I turn the heater on????????

Am I missing something here why does the heat effect the A/C compressor?

And is there any way to rebuild the pulley?

I assume there is a clutch of some sort in it.

When the heat is off it spins just fine no squeal as soon as I turn the heat on I can see the pulley stops and belt is just sliding over it. The belt is new and as tight as it can get.

Any suggestions??????????????