AC Not Working

[csheff]

I have a 99' toyota Camry with two problems. First, the a/c compressor has stopped engaging. I can jump it thru the magnetic clutch relay and is works fine. Refrigerant pressures are good. I have swapped relays to check relays. Still no go. I receive voltage to the relay, but relay will not activate in socket. Have tested with battery voltage and works fine. Pressure switch has been jumped with same results. On console, the ac switch light will not come on. I have replaced the ac switch. That is not the problem. I have checked all fuses, none bad. What else is causing it not to work?
Second problem, This may be related to the first. Now my open circuit relay is chattering very bad. Car still runs but the relay is getting very hot to the point of plastic housing starting to distort. Also have switched relays in the socket to no change in problem. What Can cause this?
Thanks

[Hajoca]

Have you taken outdoor and cabin temperatures?
Compressor does not operate in cold.

[Stillrunning]

There are two thermocouples that measure evaporator outlet and inlet temp and disengage the compressor when the air across the evaporator gets too cold, this is the on/off cycling you feel when the A/C is on and it's there to prevent frost-up. It's possible one of the thermocouples is defective. There is also an rpm counter that disengages the clutch if the engine and compressor rpms don't match - could be simple loose belt.