A/C And Heater Control Module - Operation

OPERATION

The A/C heater module utilizes integrated circuitry and information carried over the Controller Area Network (CAN) data bus to monitor many sensors and switch inputs throughout the vehicle. In response to those inputs, the internal circuitry and programming of the A/C heater module allows it to control electronic functions and features of the heating and A/C system.

Some of the inputs received by the A/C heater module over the CAN bus are as follows:

- A/C Request
- Ambient Air Temperature
- Electric Back Light (EBL) Request
- Electrical System Voltage
- Engine Coolant Temperature
- Engine Speed
- Humidity, Windshield Glass Temperature and Dewpoint (ATC only)
- Refrigerant Pressure
- Vehicle Identification Number
- Vehicle Odometer

Some of the messages broadcasted by the A/C heater module on the CAN bus are as follows:

- A/C Clutch Engage
- Auto Headlamp Signal
- EBL Status

The A/C heater module receives the following information over hardwired circuits:

- Auto Headlamp Signal
- Evaporator Temperature
- Interior Air Temperature
- Left and Right Sun Load

The A/C heater module monitors and controls the following over hardwired circuits:

- Driver and Passenger Blend Door Positions
- Blower Motor Speed
- Mode Door Position
- Recirculation Door Position

The A/C heater module is diagnosed using a scan tool. Prior to replacing an A/C heater module, run the calibration procedure to verify that the concern is not an air door calibration issue HVAC Verification Test.

The A/C heater module cannot be adjusted or repaired and must be replaced if inoperative or damaged.