OVERVIEW
The air distribution and filtering system controls the distribution and quality of air supplied into the front and rear of the cabin. The system consists of
- Air ducts
- Air registers and vents
- A cabin air filter.
Two levels of heating and ventilation are available. High specification vehicles are fitted with a dual zone automatic system, which can provide different temperature settings for the LH and RH sides of the cabin. The dual zone system may also be fitted with a pollution sensor to control the quality of air in the cabin.
Lower specification vehicles are fitted with a single zone manual system.
The heater assembly for both systems is installed on the vehicle center line, between the instrument panel and the engine bulkhead.
The ATC module controls operation of the blower motor via the blower motor control module, which is mounted on the bulkhead side of the heater assembly casing.
Refer to: Air Distribution and Filtering
Refer to: Air Conditioning
Refer to: Control Components .
Some vehicles may also be fitted with an auxiliary heater. Refer to the appropriate Electric Booster Heater and Fuel Fired Booster Heater information.
Scheme 1
Air distribution and temperature is controlled by the Automatic Temperature Control (ATC) module, which is integral with the control panel. In response to commands from the control panel, the ATC module controls operation of either 3 (single zone) or 5 (dual zone) stepper motors mounted on the heater assembly casing. See CONTROL COMPONENTS .
Scheme 2
| Item Number | Description |
|---|---|
| 1 | Blower motor control module |
| 2 | Blower motor |
| 3 | Air Conditioning (A/C) evaporator |
| 4 | Heater core |
| 5 | Electric booster heater |
The heater assembly controls the temperature of the air supplied to the air distribution ducts, as directed by the ATC module. The heater assembly is mounted on the vehicle center line and comprises the following components
- Blower motor
- Heater core
- Cabin air filter. See «AIR DISTRIBUTION AND FILTERING»(ref-531912-S26811091622013022000000) .
- A/C evaporator. See «AIR CONDITIONING»(ref-531912-S05090110422013022000000) .
- Air intake flap and stepper motor. See «CONTROL COMPONENTS»(ref-531912-S35822895042013022000000) .
- Air distribution flaps and stepper motors. See «CONTROL COMPONENTS»(ref-531912-S35822895042013022000000) .
- Temperature blend flaps and stepper motors. See «CONTROL COMPONENTS»(ref-531912-S35822895042013022000000) .
- Electric booster heater (if fitted). Refer to the appropriate Electric Booster Heater information.
PRINCIPLES OF OPERATION
Operation of the heating and ventilation system is controlled by the ATC module. See CONTROL COMPONENTS .
Scheme 3
| Item Number | Description |
|---|---|
| 1 | High pressure line |
| 2 | High pressure servicing connection |
| 3 | Low pressure servicing connection |
| 4 | Thermostatic expansion valve |
| 5 | Evaporator |
| 6 | Refrigerant pressure sensor |
| 7 | Receiver/Drier |
| 8 | Condenser |
| 9 | Air Conditioning (A/C) compressor |
| 10 | Low pressure line |
The A/C system transfers heat from the cabin to the outside atmosphere to provide the heater assembly with dehumidified cool air.
The A/C system is a sealed closed loop system, filled with a charge weight of R-134a refrigerant as the heat transfer medium. The refrigerant charge weight for both i6 and TD4 vehicles is 730 g. Oil is added to the refrigerant to lubricate the internal components of the A/C compressor.
Although different units, the A/C compressors fitted to both the i6 petrol engine and the TD4 diesel engine are both variable displacement units. The displacement (flow of refrigerant) is controlled to match the thermal load of the evaporator.
Operation of the A/C system is controlled by the Automatic Temperature Control (ATC) module. See CONTROL COMPONENTS .
To accomplish the transfer of heat, the refrigerant is circulated around the system, where it passes through 2 pressure/temperature regimes. In each of the regimes the refrigerant changes state, during which process maximum heat absorption or dissipation occurs.
The low pressure/temperature regime is from the thermostatic expansion valve, through the evaporator to the compressor. The refrigerant decreases in pressure and temperature at the thermostatic expansion valve then changes state from a liquid to a vapor in the evaporator to absorb heat.
The high pressure/temperature regime is from the compressor, through the condenser and receiver drier assembly to the thermostatic expansion valve. The refrigerant increases in pressure and temperature as it passes through the compressor, then releases heat and changes state from a vapor to a liquid in the condenser.
Operation of the A/C system is controlled by the Automatic Temperature Control (ATC) module. See CONTROL COMPONENTS .
Scheme 4
| Item Number | Description |
|---|---|
| 1 | Refrigerant pressure sensor |
| 2 | Cabin humidity sensor (if fitted) |
| 3 | Air Conditioning (A/C) compressor (i6 shown) |
| 4 | Engine Coolant Temperature (ECT) sensor |
| 5 | Ambient air temperature sensor |
| 6 | Air intake stepper motor |
| 7 | Pollution sensor (if fitted) |
| 8 | Windshield distribution (defrost) stepper motor |
| 9 | Right Hand (RH) temperature blend stepper motor |
| 10 | Sunload sensor |
| 11 | Cabin temperature sensor |
| 12 | Automatic Temperature Control (ATC) module |
| 13 | Evaporator temperature sensor |
| 14 | Left Hand (LH) temperature blend stepper motor |
| 15 | Blower motor control module |
| 16 | Face/feet distribution stepper motor |
| 17 | Blower motor |
The climate control system incorporates the heating, ventilation and A/C systems. There are 2 main types of climate control system available
- a single zone manual system
- a dual zone automatic system.
The climate control functions for both systems are controlled by the ATC module. The ATC module is mounted in the center console and contains both the system electronic software and user controls.
The ATC module works in conjunction with a number of other vehicle control modules, including the Engine Control Module (ECM), which controls a number of climate control sub-systems on receipt of requests from the ATC module.
The single zone climate control system features manual control for air temperature, air distribution and air source, although a small amount of automatic control does exist in the ATC software. In response to system inputs, the ATC module controls the operation of 3 stepper motors mounted on the heater assembly. The stepper motors then adjust the position of the air temperature, air distribution and air source flaps accordingly.
The dual zone climate control system features automatic control of air temperature, air distribution and blower motor speed. The ATC module is also able to control individual temperature requests for both the driver and passenger side of the cabin.
Note. The ATC module can only maintain a maximum temperature difference between the 2 sides of the cabin of up to approximately 3°C (4°F). This is due to the movement and mix of air within the cabin.
The dual zone climate control system features 2 additional sensors; a cabin temperature sensor and a sunload sensor. The cabin temperature sensor provides a temperature feedback to enable the ATC module software maintain a constant cabin temperature. The sunload sensor provides a reading of solar loading on the vehicle occupants and enables the ATC module to adjust the output from the climate control system accordingly.
Higher specification versions of the dual zone climate control system are also available. These systems feature 2 more additional sensors; a pollution sensor and a cabin humidity sensor.
The pollution sensor detects pollutants entering the cabin, allowing the ATC module to react by changing the position of the air intake flap. The cabin humidity sensor calculates the probability of misting on the windshield. The ATC module monitors the signal from the cabin humidity sensor and adjusts blower speed, air distribution and A/C compressor displacement accordingly.