A/C Pressure Sensors
WARNING: This page does not describe the selected car, but rather 7 other vehicles, including the 2002 GMC Yukon XL, 2002 GMC Yukon, 2002 Chevrolet Tahoe, 2002 Chevrolet Suburban, and 2002 Chevrolet Avalanche. However, it is still accessible from the selected car via links, so may be relevant.
The A/C system is protected by 2 pressure switches. The A/C high pressure switch interrupts the A/C request signal when the A/C line pressure exceeds 420 psi (2896 kPa). The A/C low pressure switch interrupts the A/C low pressure switch signal when the A/C line pressure falls below 21-25 psi (145-172 kPa). When the PCM sees an open in either signal, the A/C clutch relay control circuit is no longer grounded, thus shutting off the compressor. The low pressure switch will close when pressure reaches 38-42 psi (262-290 kPa).