To update in case anyone wonders; I swapped out compressors and the system functions perfectly.

Thanks for the reply. Yes it is an A6 compressor installed on a 1972 Corvette.

I charged an R12 system today that hasn't been used in a couple years. The evaporator and dryer are new, the compressor and condenser are original. The POA valve is also original but bench tested good. the expansion valve is original and reconditioned by Original Air. The ambient temperature was 85 ...