HVAC Control System Description

HVAC Control System Description

Following data are sent from each control module to the HVAC control module through CAN communication. For CAN communication system, refer to description on Communication System Description.
- Engine coolant temperature
- Engine speed
- A/C refrigerant pressure
- Vehicle speed (wheel speed)
- Outside air temperature
- Evaporator temperature
- A/C compressor clutch state

Based on above data, HVAC control module sends A/C compressor ON / OFF request signal to ECM through CAN communication.
Furthermore, when the defrost switch is turned on or the "MODE" (air flow) switch is selected to "D/F" mode, HVAC control module sends A/C compressor ON request signal to BCM through CAN communication to clear fog from windshield.
BCM sends this signal through CAN communication to ECM which then causes A/C compressor relay to turn ON / OFF.
For more information on signal transmission and reception of Auto A/C system, refer to HVAC Electronic Control Input / Output Block Diagram.