Q: A/c

A/c stopped working on long cross-country trip. Had entire system replaced by professional( compressor, drier, orifice. System has been intermittent since then. Worked for a solid month no problems when temp was 90+ then intermittent again. Pulled climate control board off another car and that seemed to resolve it for a little while but is intermittent again. I've played with it quite a bit b/c the guy that installed basically threw up his hands. Compressor usually if not always comes on when car is started from cold. I've left it in park at this point and the compressor stays on. Once driven usually becomes intermittent. The interesting part is I can force the problem by shutting the compressor off, allowing the low side to pressure back up. At this point the compressor will almost never restart.

My car has 125000 miles.
My car has an automatic transmission.