A/C Compressor Clutch Relay

WARNING: This page is about a different car, the 2003 Pontiac Vibe. However, it is still accessible from the selected car via links, so may be relevant.

Pressing the A/C button enables the PCM to request A/C compressor engagement and illuminate the A/C indicator. The A/C button sends a signal to the PCM for A/C compressor engagement. The PCM will provide a ground for the A/C compressor clutch relay enabling it to close its internal contacts to send battery voltage to the A/C compressor clutch coil. The A/C compressor diode will prevent a voltage spike, resulting from the collapse of the magnetic field of the coil, from entering the vehicle electrical system when the compressor is disengaged. Defrost and Defog mode selections will request A/C operation but not turn on the A/C indicator. The blower switch must be in any position except OFF for the A/C system to operate. The A/C system can operate regardless of the temperature control setting. The following conditions must be met in order for the A/C compressor clutch to turn on:

Ambient air temperature above 40°F (4°C).
A/C refrigerant pressure switch parameters are met.
PCM receives an A/C request from the A/C switch.
Engine coolant temperature is less than 250°F (121°C).
Engine speed is more than 550 RPM.
Throttle position is less than 100 percent.