Heating & A/C Operation
The purpose of the heating and A/C system is to provide heated and cooled air to the interior of the vehicle. The A/C system will also remove humidity from the interior and reduce windshield fogging. The vehicle operator can determine the passenger compartment temperature by adjusting the air temperature switch. Regardless of the temperature setting, the following can effect the rate that the HVAC system can achieve the desired temperature:
- Recirculation
- Difference Between Inside And Desired Temperature
- Difference Between Ambient And Desired Temperature
- Blower Motor Speed Setting
- Mode Setting
The PCM will operate the A/C system automatically in FRONT DEFROST mode to help reduce moisture inside the vehicle. The A/C LED will illuminate when the driver presses the A/C request switch and when FRONT DEFROST mode is selected. The following conditions must be met in order for the PCM to turn on the compressor clutch:
- BCM - Battery voltage between 9-18 volts and A/C request from the HVAC control assembly.
- PCM - Engine Coolant Temperature (ECT) is less than 250°F (121°C), engine speed is less than 5000 RPM and A/C pressure is between 432-27 psi (2979-186 kPa).
Once engaged, the compressor clutch will be disengaged for the following conditions:
- Throttle position is 100 percent.
- A/C Pressure is more than 432 psi (2979 kPa).
- A/C Pressure is less than 27 psi (186 kPa).
- Engine Coolant Temperature (ECT) is more than 250°F (121°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.