A/C Request Signal
WARNING: This page is about a different car, the 2003 Pontiac Grand Prix, 2003 Chevrolet Malibu, and 2003 Buick Century. However, it is still accessible from the selected car via links, so may be relevant.
The A/C system can be engaged when the VENT switch is pressed or the HVAC control module is in FRONT DEFROST, MIX-BLEND mode or during automatic operation. The HVAC control module sends a Class 2 A/C request message to the Powertrain Control Module (PCM). The following conditions must be met in order for the PCM to turn on the compressor clutch:
- HVAC Control Module - Ambient temperature is more than 40°F (4°C).
- PCM - Engine Coolant Temperature (ECT) is less than 255°F (124°C), Engine speed is less than 5000 RPM and A/C Pressure is 410-30 psi (2826-207 kPa).
Once engaged, the compressor clutch will be disengaged for the following conditions:
- Throttle position is 100 percent.
- A/C Pressure is more than 410 psi (2826 kPa).
- A/C Pressure is less than 30 psi (207 kPa).
- ECT is more than 255°F (124°C).
- Engine speed is more than 5000 RPM.
- Transmission shift.
- PCM detects excessive torque load.
- PCM detects insufficient idle quality.
- PCM detects a hard launch condition.
When the compressor clutch disengages, the compressor clutch diode protects the electrical system from a voltage spike.