2000 Pontiac Grand Prix A/C Compressor not coming on

When I turn on my a/c the compressor does not come on. The exterior temp sensor reads normal via the a/c control panel, the a/c system has enough refrigerant and reads about 20-25psi pressure when I jump the clutch relay for the compressor and the ac starts to work and blows plenty cold. I switched the realys with the fog light relay and the fog lights still work but the clutch never engages. Im thinking its a pressure switch not reading enough refrigerant pressure keeping the compressor from coming on. The ac light on the ac panel does come on and stays on but i get no cold air. what do you guys think? thanks