1999 Millenia AC Electrical Problem
 

My AC compressor is not coming on when AC is selected. Freon system is good so I have an electical problem. I have the dash apart and a wiring diagram for the AC circuit.
I need help in a couple of areas.
1) Does anybody have info that tells what conditions must be met for the AC to come on (ie: which sensors?)?
2) The PCM(Powertrain Control Module) is in the circuit. It is right down at the bottom of the centre of the dash. I am having trouble getting it out. I have the screws out at the face and each side near the rear but there isn't enough slack in the cables to pull it out or get at the cables to disconnect them.