Low Pressure Switch

[1stPontiac]

Hi I have a 2005 Pontiac Grand Prix GXP and i'm having problems with my A/C system.  I just purchased this car a month ago and when i tried to turn the a/c on nothing would happen. They system has good standing pressure so I know that there's refrigerant in the system. I have located the HPS but cannot find the LPS.  I was able to get the clutch to come on and off again by taking the HPS off and then put it back on and that would start the clutch for a few seconds then cut off.  All the fuses are good in the car but I'm at a loss. Can someone point me in a direction to start at, Is there a LPS to look at.  Thanks for the help