Control Module HVAC: Description and Operation

General Description

Location:

The A/CCM is located on the right hand side of the air conditioning unit and controls all system functions.

The temperature within the passenger compartment is continually compared with the temperature selected on the control panel LCD. The A/CCM receives data input signals and compares these with signals from the system temperature sensors and feedback devices. Based on this information the A/CCM adjusts the air outlet temperature, airflow and distribution from the air conditioning system into the passenger compartment.

Identification:

Inputs/Outputs
1. Engine speed:
Input to the A/CCM from the ECM.

Heated windshield and backlight will be inhibited when engine speed <50 RPM.

2. Vehicle speed:
Input from the instrument cluster.

Blower speed control to minimize the effects of ram air. Road speed compensation is inhibited when maximum cooling LO, or maximum heating HI, is selected; also inhibited in defrost mode with airflow set to maximum.

Used to determine the frequency at which the exterior temperature display is updated.

3. Coolant temperature (signal derived from ECM via instrument cluster):
Input from the heater matrix temperature sensor used to control water valve and thus vent temperatures.

Used to monitor the temperature of coolant at the heater matrix to assist the control of air outlet temperature.

Used to inhibit the blowers when heating is selected and the engine coolant temperature is below 30° C.

Is used to provide progressive increase in blower speed up to 60° C.

To inhibit the water valve and pump when the coolant temperature is = <10° C