1990 Q45 A/C Problem

Just put in a rebuilt A/C compressor (last one clutch locked up) and a new dryer. I had it evacuated and recharged but the compressor won't come on now. A/C mechanic says he has checked everything. The relay for the compressor is getting a signal from the pressure switch connected to the dryer but he says that the signal from the hvac unit/computer isn't telling the compressor to come on. Anyone heard of that?
I saw him testing it and when he cheated that input the compressor would start. I am also having a problem with my hvac control in that it will only blow out of the vents. I can change the setting to heater or defrost, the screen changes but the air flow doesn't, I hear something actuate in the dash, but that's it. It still comes out of the vents. This has happened before but it just started working on it's own one day.
I changed the hvac control unit months ago because the last one would not light up but the intermittant problem with air flow has come back. Any ideals? Can these 2 problems be related? I live in Florida and the car is black. Driving around hot isn't the worse problem. It's worse when it rains and I can't defrost/clear the windows. It's down right dangerous.