A/C Request Signal

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.