Module, A/C And Heater: 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. Vehicles equipped with the A/C heater module are not equipped with a separate Heating, Ventilation and Air Conditioning (HVAC) module. 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 HVAC 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
• Refrigerant Pressure
• Vehicle Identification Number
• Vehicle Odometer

Some of the messages broadcast 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
• 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. Refer to HVAC VERIFICATION TEST .

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