HVAC System Description
In the automatic air conditioning system (auto A/C), HVAC control module automatically controls inside air temperature of the driver side and the passenger side, blower speed, air inlet and outlet, etc. Once users set desired inside air temperature with the temperature control selector and push "AUTO" switch, HVAC control module starts detecting the inside air temperature, the outside air temperature, sunlight of the driver side and the passenger side and the engine coolant temperature by means of the inside air temperature sensor, the outside air temperature sensor, the sunload sensor (driver side and passenger side detecting type), and the engine coolant temperature (ECT) sensor, respectively. When "DUAL" switch is at ON, the temperature of each driver side and passenger side can be selected, respectively. However, when "DUAL" switch is at OFF, selected temperature in the driver side is applied to the passenger side as well.
In this way, HVAC control module keeps in-car temperature at the desired level at all times.
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 .
A/C Operation Description at ECM
When ECM receives A/C switch ON signal sent from HVAC control module via CAN communication system, it controls A/C compressor relay and radiator (condenser) cooling fan relay. The A/C switch ON signal from HVAC control module is transmitted to ECM through BCM. For CAN communication system, refer to COMMUNICATION SYSTEM DESCRIPTION .
On-Board Diagnostic System Description
HVAC control module detects malfunctions, which may occur in the following areas
- Inside air temperature sensor
- Sunload sensor
- CAN communication line
- LIN communication line
- Serial communication line
- Driver side temperature control actuator
- Passenger side temperature control actuator
- Air flow control actuator
- Air intake control actuator
- Auto A/C panel
- HVAC control module
When HVAC control module detects malfunction, the "AUTO" display (1) flashes to warn and the diagnostic trouble code (DTC) is stored in the memory of the module. When diagnosing trouble, the DTC can be checked with DTC CHECK .
Scheme 1
CAN Communication System Description
HVAC control module communicates with other control modules through CAN communication. For CAN communication, refer to COMMUNICATION SYSTEM DESCRIPTION .
