Control Module HVAC: Description and Operation

HVAC CONTROL MODULE




The HVAC control module is a non-class 2 device that interfaces between the operator and the HVAC system to maintain air temperature and distribution settings. The battery positive voltage circuit provides power to the control module. The ignition 3 voltage circuit provides a device on signal to the HVAC control module. The control module supports the features as in the table.

Upon initial ignition ON after a battery disconnect the HVAC control module will calibrate the air temperature and mode actuators. The next ignition cycle the HVAC control module takes the follow actions:
- The HVAC control module will first perform required memory diagnostics. If there is fault, then A/C request will be disabled and the recirculation door position will be defaulted to outside air position
- Restore the A/C state from memory
- Restore the recirculation actuator position from memory
- Set the rear defrost output to OFF
- Set the blower motor speed to the actual blower motor switch position
- Set the mode door position to the actual mode switch position
- Set the air temperature door position to the actual air temperature switch position

Diagnostic trouble codes (DTC) are manually retrieved and cleared through the HVAC control module. Refer to Diagnostic Trouble Code (DTC) Displaying or Diagnostic Trouble Code (DTC) Clearing.