Compressor Rebuild

Zombie thread alert, I'm bringing this one back from the dead....

Bob, did you ever rebuild the compressor with success, I have my A/c system done but as I charge it to the correct psi with coolant, it slows the compressor down and starts to spin the belt. The only thing I can think of is maybe there is a valve that's bad inside the compressor that is letting pressure build up where it's not supposed to.
The A/C is cool but not cold because it's only charged to 20psi ( temp at the vent is 55* with the fan on low and 70 with the fan on high. )