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 CAN Communication System Description CAN Communication System Description.

- Engine coolant temperature
- Engine speed
- A/C refrigerant pressure
- Vehicle speed (wheel speed)
- Outside air temperature
- A/C compressor clutch state

Based on evaporator temperature sensor signal and above data, HVAC control module sends A/C compressor ON / OFF request signal to BCM through CAN communication.

Furthermore, when the defrost switch is turned on or the "MODE" (air flow) selector is selected to "D/F" mode, HVAC control module sends A/C compressor ON request signal to BCM through CAN communication to clear fogging from windshield.

BCM sends this signal through CAN communication to ECM which then causes compressor relay to turn ON / OFF.

For more information on signal transmission and reception of Auto A/C system, refer to Auto A/C Electronic Control Input / Output Diagram Auto A/C Electronic Control Input / Output Diagram.

HVAC control module has a function to make initial settings of temperature control actuator, air intake actuator and air flow actuator.

Initial settings of actuators are automatically made when engine is started for the first time after battery is connected.

When initial settings are made, each actuator is forced to operate for about 15 seconds continuously.