Face Level Registers
Operation of the face level registers is controlled by the automatic temperature control (ATC) module, using local interconnect network (LIN) bus messages to the integral stepper motors. The four registers operate together in both the opening and closing phases.
The face level registers can be selected to run in one of two modes; 'automatic' or 'always open'. The mode is selected on the climate control screen of the TSD. Refer to Navigation System or Navigation System information.
In the automatic mode, operation of the face level registers is synchronized with the engine START/STOP button. When the engine starts the automatic temperature control (ATC) module opens the registers. When the engine stops, the automatic temperature control (ATC) module closes the registers.
If a face level register is fouled, when it receives an open or close request, the register concerned makes a number of attempts to reach the requested position. If the register still does not move, it is left in the fouled position. The remaining registers will continue to open and close as normal.
The automatic mode is disabled when the climate control system is off. The automatic temperature control (ATC) module closes the registers if they are open in the automatic mode and the climate control system is selected off.
Air Ducts
The air ducts distribute air from the heater assembly to the registers and vents in the instrument panel and the center floor console. Air ducts also direct air from the heater assembly into the front and rear footwells.
Registers and Vents
The registers control the flow and direction of air from the air ducts. The instrument panel contains four face level registers; one at each end and two mounted centrally. For the rear seat occupants, two registers are installed in the rear face of the center floor console. All of the registers incorporate vertical and horizontal directional vane adjustment and full air flow adjustment down to zero.
The four face level registers in the instrument panel each contain an integral stepper motor. The stepper motors enable the registers to rotate between the open and closed positions. In the open position, the registers have normal appearance and functionality. In the closed position, the registers present a smooth surface flush with the surrounding instrument panel.
The vents are fixed outlets. There are four vents in the upper surface of the instrument panel; one in each end to direct air onto the side windows and two along the front edge to direct air onto the windshield.
| Item Number | Description |
|---|---|
| A | Registers closed |
| B | Registers open |
Pollen Filter
Note. left-hand drive (LHD) vehicle shown, right-hand drive (RHD) vehicle similar.
| Item Number | Description |
|---|---|
| 1 | Air inlet duct |
| 2 | Pollen filter |
| 3 | Cover |
The pollen filter removes odors and fine particles from fresh air entering the passenger compartment. The pollen filter is located in the air inlet duct, in the inlet to the blower. A cover on the underside of the air inlet duct provides access to the pollen filter for servicing.
Air Inlet Duct
The air inlet duct connects the fresh air inlet in the engine bulkhead to the heater assembly. The air inlet duct is installed behind the instrument panel on the passenger side.
The air inlet duct consists of a casing that contains a pollen filter, an air inlet door, a blower and a blower control module. A recirculation air inlet is incorporated into the casing. A servo motor is mounted on the casing and connected to the air inlet door, to allow selection between fresh and recirculated air. See Control Components .
The pollen filter is part of the air distribution and filtering system. See Air Distribution and Filtering .
The blower regulates the volume of air flowing through the air inlet duct to the heater assembly. The blower consists of an open hub, centrifugal fan and an electric motor.
The blower control module regulates the power supply to the blower motor. The blower control module is installed in the air inlet duct downstream of the blower, where any heat generated during operation is dissipated by the air flow.
Auxiliary Coolant Pump
On all vehicles except 3.0L, an auxiliary coolant pump is installed on the rear right side of the radiator housing, in the return line from the heater core. The auxiliary coolant pump is an electric pump that boosts the flow of coolant through the heater core.
Ventilation Outlets
The ventilation outlets allow the free flow of air through the passenger compartment. The outlets are installed in the LH and RH rear quarter panels, below the rear lamps. Each ventilation outlet consists of a grille covered by a soft rubber flap, and is effectively a non-return valve. The flaps open and close automatically depending on the pressure differential between the air inside and outside the vehicle.
General
To accomplish the transfer of heat, refrigerant is circulated around a sealed system, where it passes through two 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 air conditioning (A/C) system is controlled by the automatic temperature control (ATC) module. See Control Components .
The air conditioning (A/C) system works in conjunction with
- The air distribution and filtering system. See «Air Distribution and Filtering»(ref-568412-S00413474842013072200000) .
- The heating and ventilation system. See «Heating and Ventilation»(ref-568412-S21930483842013072200000) .
A/C System Flow Diagram
Note. A = Refrigerant liquid; B = Refrigerant vapor; C = Air flow.
| Item Number | Description |
|---|---|
| 1 | Evaporator |
| 2 | Thermostatic expansion valve |
| 3 | High pressure servicing connection |
| 4 | Refrigerant pressure sensor |
| 5 | Engine cooling fan |
| 6 | Condenser |
| 7 | Receiver/Drier |
| 8 | Air conditioning (A/C) compressor |
| 9 | Low pressure servicing connection |
| 10 | Blower |
A/C Compressor
| Item Number | Description |
|---|---|
| 1 | Pressure relief valve |
| 2 | Outlet port |
| 3 | Inlet port |
| 4 | Solenoid valve |
| 5 | Electrical connector |
| 6 | Pulley |
The air conditioning (A/C) compressor circulates refrigerant around the system by compressing low pressure, low temperature vapor from the evaporator and discharging the resultant high pressure, high temperature vapor to the condenser.
The air conditioning (A/C) compressor is a permanently engaged variable displacement unit which is driven by the engine accessory drive belt. To protect the system from excessive pressure, a pressure relief valve is installed in the outlet side of the air conditioning (A/C) compressor. The pressure relief valve vents excess pressure into the engine compartment.
Condenser
| Item Number | Description |
|---|---|
| 1 | Right-hand (RH) end tank |
| 2 | Condenser core |
| 3 | Left-hand (LH) end tank |
| 4 | Mounting brackets (4 off) |
| 5 | High pressure compressor discharge line connector block |
| 6 | High pressure liquid outlet line connector block |
| 7 | Receiver/Drier outlet pipe |
| 8 | Receiver/Drier inlet pipe |
| 9 | Receiver/Drier |
The condenser transfers heat from the refrigerant to the surrounding air to convert the high pressure vapor from the compressor into a liquid. The condenser is installed immediately in front of the radiator. Two brackets on each end tank attach the condenser to the end tanks of the radiator.
The condenser is classified as a sub-cooling condenser and consists of a fin and tube heat exchanger core installed between two end tanks. Divisions in the end tanks separate the heat exchanger into a four pass upper (condenser) section and a two pass lower (sub-cooler) section.
The left-hand (LH) end tank provides the connections to the high pressure line from the air conditioning (A/C) compressor and the high pressure liquid line to the evaporator.
The right-hand (RH) end tank provides the connections to the receiver drier.
Receiver Drier
The receiver drier is integrated into the right-hand (RH) end tank of the condenser to remove solid impurities and moisture from the refrigerant. It also provides a reservoir for liquid refrigerant to accommodate changes of heat load at the evaporator.
Note. The receiver drier is part of the condenser assembly and is not serviceable separately.
Refrigerant entering the receiver drier passes through a filter and a desiccant pack, then collects in the base of the unit before flowing through the outlet pipe back to the condenser.
Refrigerant Pressure Sensor
The refrigerant pressure sensor is located in the high pressure/temperature refrigerant line between the condenser and the thermostatic expansion valve. See Control Components .
Thermostatic Expansion Valve
| Item Number | Description |
|---|---|
| 1 | Metering valve |
| 2 | Housing |
| 3 | Diaphragm |
| 4 | Temperature sensor |
| 5 | Outlet passage from evaporator |
| 6 | Inlet passage to evaporator |
The thermostatic expansion valve meters the flow of refrigerant into the evaporator, to match the refrigerant flow with the heat load of the air passing through the evaporator.
The thermostatic expansion valve is a block type valve located behind the heater assembly, and attached to the inlet and outlet ports of the evaporator. The thermostatic expansion valve consists of an aluminum housing containing inlet and outlet passages. A ball and spring metering valve is installed in the inlet passage and a temperature sensor is installed in the outlet passage. The temperature sensor consists of a temperature sensitive tube connected to a diaphragm. The bottom end of the temperature sensitive tube acts on the ball of the metering valve. Pressure on top of the diaphragm is controlled by the evaporator outlet temperature conducted through the temperature sensitive tube. The bottom of the diaphragm senses evaporator outlet pressure.
Liquid refrigerant flows through the metering valve into the evaporator. The restriction across the metering valve reduces the pressure and temperature of the refrigerant. The restriction also changes the liquid stream of refrigerant into a fine spray, to improve the evaporation process. As the refrigerant passes through the evaporator, it absorbs heat from the air flowing through the evaporator. The increase in temperature causes the refrigerant to vaporize and increase in pressure.
The temperature and pressure of the refrigerant leaving the evaporator acts on the diaphragm and temperature sensitive tube, which regulate the metering valve opening and so control the volume of refrigerant flowing through the evaporator. The warmer the air flowing through the evaporator, the more heat available to evaporate refrigerant and thus the greater volume of refrigerant allowed through the metering valve.
Evaporator
The evaporator is installed in the heater assembly, between the blower and the heater matrix, to absorb heat from the exterior or recirculated air.
Most of the moisture in the air passing through the evaporator condenses into water, which drains out of the vehicle by passing through a drain tube to the underside of the vehicle.
Refrigerant Lines
To maintain similar flow velocities around the air conditioning (A/C) system, the diameter of the refrigerant lines varies to suit the two pressure/temperature regimes. Larger diameter pipes are installed in the low pressure/temperature regime and smaller diameter pipes are installed in the high pressure/temperature regime.
Low and high pressure charging connections are incorporated into the refrigerant lines for system servicing.
Air Inlet Control
The source of inlet air is automatically controlled unless overridden by pressing the air recirculation switch on the integrated control panel. During automatic control, the automatic temperature control (ATC) module determines the required position of the recirculation door from its 'comfort' algorithm and, if fitted, the pollution sensor.
The automatic temperature control (ATC) module provides analogue signals to the air inlet servo motor along a hardwired connection. A potentiometer in the motor supplies the automatic temperature control (ATC) module with a position feedback signal for closed loop control.
Air Temperature Control
Cooled air from the evaporator enters the heater assembly, where temperature blend doors direct a proportion of the air through the heater core to produce the required output air temperature.
The two temperature blend doors operate independently to enable individual temperature settings for the left and right sides of the passenger compartment. The temperature blend doors are operated by stepper motors, which are controlled by the automatic temperature control (ATC) module using local interconnect network (LIN) bus messages.
The automatic temperature control (ATC) module calculates the temperature blend stepper motor positions required to achieve the selected temperature and compares it against the current position. If there is any difference, the automatic temperature control (ATC) module signals the stepper motors to adopt the new position.
Air temperature is controlled automatically unless maximum heating (HI) or maximum cooling (LO) is selected. When maximum heating or cooling is selected, a 'comfort' algorithm in the automatic temperature control (ATC) module adopts an appropriate strategy for air distribution, blower speed, and air source.
Temperature control in one side of the passenger compartment can be compromised by the other side of the passenger compartment being set to a high level of heating or cooling. True maximum heating or cooling (displayed as 'HI' or 'LO' on the TSD) can only be selected for the driver's side of the passenger compartment. If 'HI' or 'LO' is selected for the driver's side, the temperature for the front passenger's side is automatically set to match the driver's side.
If air conditioning (A/C) is selected off in the automatic mode, no cooling of the inlet air will take place. The minimum output air temperature from the system will be ambient air temperature plus any heat pick up in the air inlet path.
If the Temp. sync. soft button on the TSD is pressed, the automatic temperature control (ATC) module synchronizes the temperature of the passenger side of the passenger compartment with the driver's side.
Blower Control
When the system is in the automatic mode, the automatic temperature control (ATC) module determines the blower speed required from a comfort algorithm. When the system is in the manual mode, the automatic temperature control (ATC) module operates the blower at the speed selected using either the rotary control switch on the integrated control panel or the + and - soft buttons on the touch screen display (TSD). The automatic temperature control (ATC) module also adjusts blower speed to compensate for the ram effect on inlet air produced by forward movement of the vehicle. As vehicle speed and ram effect increases, blower motor speed is reduced, and vice versa.
Air Distribution Control
Two air distribution doors are used to direct air into the passenger compartment. The doors are operated by stepper motors, which are controlled by the automatic temperature control (ATC) module using local interconnect network (LIN) bus messages.
When the air conditioning (A/C) system is in automatic mode, the automatic temperature control (ATC) module automatically controls air distribution into the passenger compartment in line with its 'comfort' algorithm. Automatic control is overridden if any of the TSD air distribution soft buttons are selected. Air distribution in the passenger compartment will remain as selected until the 'Auto' switch is pressed or a different manual selection is made.
A/C Compressor Control
When air conditioning (A/C) is selected the automatic temperature control (ATC) module maintains the evaporator at an operating temperature that varies with the passenger compartment cooling requirements. If the requirement for cooled air decreases, the automatic temperature control (ATC) module raises the evaporator operating temperature by reducing the flow of refrigerant provided by the air conditioning (A/C) compressor. The automatic temperature control (ATC) module closely controls the rate of temperature increase to avoid introducing moisture into the passenger compartment.
If the requirement for cooled air increases, the automatic temperature control (ATC) module lowers the evaporator operating temperature by increasing the flow of refrigerant provided by the air conditioning (A/C) compressor.
When air conditioning (A/C) is off, the compressor current signal supplied by the automatic temperature control (ATC) module holds the air conditioning (A/C) compressor solenoid valve in the minimum flow position, effectively switching off the air conditioning (A/C) function.
The automatic temperature control (ATC) module incorporates limits for the operating pressure of the refrigerant system. If the system approaches the high pressure limit, the compressor current signal is progressively reduced until the system pressure decreases. If the system falls below the low pressure limit, the compressor current signal is held at its lowest setting so that the air conditioning (A/C) compressor is maintained at its minimum stroke. This avoids depletion of the lubricant from the air conditioning (A/C) compressor.
Cooling Fan Control
The automatic temperature control (ATC) module determines the amount of condenser cooling required from the refrigerant pressure sensor, since there is a direct relationship between the temperature and pressure of the refrigerant. The cooling requirement is broadcast to the engine control module (ECM) on the medium speed controller area network (CAN) bus. The engine control module (ECM) then controls the temperature of the condenser using the cooling fan.
Programmed Defrost
The programmed defrost DEF switch is located on the integrated control panel. When the switch is pressed, the automatic temperature control (ATC) module instigates the programmed defrost function. When selected, the automatic temperature control (ATC) module configures the system as follows
- Automatic mode off.
- Air conditioning (A/C) on.
- Selected temperature unchanged.
- Air inlet set to fresh air.
- Air distribution set to windshield.
- Blower speed set to level 6.
- Windshield heater (where fitted) and rear window heater on.
The programmed defrost function can be cancelled by one of the following
- Selecting any air distribution switch on the TSD.
- Pressing the AUTO switch on the integrated control panel.
- A second press of the DEF button.
- Switching the ignition OFF.
The blower speed can be adjusted without terminating the programmed defrost function.
Rear Window Heater
Rear window heater operation is only enabled when the engine is running. The automatic temperature control (ATC) module controls operation of the rear window heater using a relay in the rear junction box (RJB). When rear window heater operation is required, the automatic temperature control (ATC) module broadcasts a message to the rear junction box (RJB) on the medium speed controller area network (CAN) bus. On receipt of the message, the rear junction box (RJB) energizes the relay by providing a ground path for the relay coil. This allows a battery feed to flow across the relay to power the rear window heater element.
There are two modes of rear window heater operation; manual and automatic.
Manual operation is activated by pressing the rear window heater switch on the integrated control panel. When the switch is pressed, the status light emitting diode (LED) in the switch illuminates and the rear window heater element is energized. Manual operation is discontinued when the rear window heater switch is pressed a second time, 21 minutes have elapsed (the heating phase), or the engine stops. If manual operation is discontinued by the engine stopping, the previous heating phase is resumed if the engine is re-started within 30 seconds.
There are two variants of automatic operation; automatic operation at the start of a journey and automatic operation during a journey.
Automatic operation at the start of a journey is initiated if the ambient air temperature is below 5 °C (41 °F). In this instance, the switch light emitting diode (LED) is illuminated and the heater element is energized for 21 minutes. Automatic operation is discontinued if the rear window heater switch is pressed or the engine stops.
Automatic operation during a journey is initiated when low ambient air temperatures are experienced and the vehicle has been travelling for a set period of time above a threshold speed. In this instance, no feedback is given to the driver to inform him the rear window heater is operational (the switch light emitting diode (LED) is not illuminated). The duration of heater operation is variable depending on the ambient air temperature, vehicle speed and the amount of time the vehicle has been travelling.
Windshield Heater (Where Fitted)
Windshield heater operation is only enabled when the engine is running. The automatic temperature control (ATC) module controls operation of the windshield heater using two relays in the engine junction box (EJB). When windshield heater operation is required, the automatic temperature control (ATC) module broadcasts a message to the central junction box (CJB) on the medium speed controller area network (CAN) bus. On receipt of the message, the central junction box (CJB) energizes the relays by providing a ground path for both relay coils. This allows a battery feed to flow across the relays to power the windshield left and right heater elements.
There are two modes of windshield heater operation; manual and automatic.
Manual operation is activated by pressing the windshield heater switch on the integrated control panel. When the switch is pressed, the status light emitting diode (LED) in the switch illuminates and the windshield heater elements are energized. Manual operation is discontinued when the windshield heater switch is pressed a second time, 5 minutes have elapsed (the heating phase), or the engine stops. If manual operation is discontinued by the engine stopping, the previous heating phase is resumed if the engine is re-started within 30 seconds.
There are two variants of automatic operation; automatic operation at the start of a journey and automatic operation during a journey.
Automatic operation at the start of a journey is initiated if the ambient air temperature is below 5 °C (41 °F). In this instance, the switch light emitting diode (LED) is illuminated and the heater elements are energized for 6.5 minutes. Automatic operation is discontinued if the windshield heater switch is pressed or the engine stops.
Automatic operation during a journey is initiated when low ambient air temperatures are experienced and the vehicle has been travelling for a set period of time above a threshold speed. In this instance, no feedback is given to the driver to inform him the windshield heater is operational (the switch light emitting diode (LED) is not illuminated) and the duration of operation is variable depending upon the ambient air temperature, vehicle speed and the amount of time the vehicle has been travelling.
Exterior Mirror Heaters
Operation of the exterior mirror heaters is fully automatic and not controllable by the driver. Exterior mirror heater operation is determined by ambient air temperature and windshield wiper status. When ambient air temperature reaches a pre-determined level, the automatic temperature control (ATC) module broadcasts an exterior mirror heating request to the door modules over the medium speed controller area network (CAN) bus. On receipt of this message, the door modules provide feed and ground connections to both exterior mirror heater elements.
The amount of time the exterior mirror heaters are operational increases if the windshield wipers are switched on. This ensures the mirrors remain mist free in damp and wet conditions, where there is an increased risk of misting.
Seat Heaters (Where Fitted)
There are four seat heater settings available; off, 1, 2 and 3, which can be selected on the home and climate control screens of the TSD. The heat setting is relayed to the vehicle occupants through a graduated display on the TSD.
Operation of the heated seats is controlled by the automatic temperature control (ATC) module. When the automatic temperature control (ATC) module receives a heating request from the TSD, it broadcasts a message to the central junction box (CJB) over the medium speed controller area network (CAN) bus. The central junction box (CJB) then provides a hardwired 12 V supply to the three heater elements in the related front seat. The heater elements, two in the seat cushion and one in the seat squab, are wired in series. The automatic temperature control (ATC) module monitors seat temperature using a temperature sensor located in each seat cushion. The central junction box (CJB) provides the temperature sensors with a 5 V supply. The level of the returned voltage back to the central junction box (CJB) is proportional to the seat temperature. The value of the return signal is broadcast to the automatic temperature control (ATC) module, over the medium speed controller area network (CAN) bus, which allows it to control the seat temperature to the required level. The automatic temperature control (ATC) module will suspend or disable operation of the seat heaters if any of the following occur
- Battery voltage exceeds 16.5 ± 0.3 V for more than 5 seconds. Seat heating is re-enabled when battery voltage decreases to 16.2 ± 0.3 V.
- If a short or open circuit is detected.
- If the seat heat temperature rises significantly above the target temperature setting.
The graduated display on the TSD remains illuminated until the seat heaters are turned off or the engine stops. If the engine is restarted within 30 seconds the seat heater resumes the previous heating level.
Steering Wheel Heater
The steering wheel heater has a single heat setting and is turned on/off on the home and climate control screens of the TSD. The on/off status of the steering wheel heater is relayed to the vehicle occupants through the TSD. When the ignition is switched off, the steering wheel heater will reset to off.
Power for the heater element is supplied by the central junction box (CJB) on receipt of a request from the automatic temperature control (ATC) module over the medium speed controller area network (CAN) bus. Temperature control for the heater element is provided by the steering wheel heater control module which receives a temperature feedback signal from a negative temperature coefficient (NTC) thermistor located within the steering wheel.
ATC Module
The automatic temperature control (ATC) module is mounted on the outboard end of the air inlet duct, behind the front passenger side of the instrument panel. The automatic temperature control (ATC) module processes inputs from the TSD, the switches on the integrated control panel and the system sensors. In response to these inputs, the automatic temperature control (ATC) module outputs control signals to the air conditioning (A/C) system and the heating and ventilation system.
Two electrical connectors provide the interface between the automatic temperature control (ATC) module and the vehicle wiring. The automatic temperature control (ATC) module uses hardwired inputs from the system sensors, the local interconnect network (LIN) bus to communicate with the stepper motors and the medium speed controller area network (CAN) bus to communicate with other control modules on the vehicle.
A/C Compressor Solenoid Valve
The air conditioning (A/C) compressor solenoid valve is integral with the air conditioning (A/C) compressor. Operation of the solenoid valve is controlled by the automatic temperature control (ATC) module using a hardwired drive current of differing values. By controlling the flow of refrigerant through the compressor, the solenoid valve can control the air conditioning (A/C) system pressure and the evaporator operating temperature.
The refrigerant pressure sensor provides the automatic temperature control (ATC) module with a pressure input from the high pressure side of the refrigerant system. The refrigerant pressure sensor is located in the refrigerant line between the condenser and the thermostatic expansion valve.
The automatic temperature control (ATC) module supplies a 5 V reference voltage to the refrigerant pressure sensor and receives a return signal voltage, between 0 V and 5 V, related to system pressure.
The automatic temperature control (ATC) module uses the signal from the pressure sensor to protect the refrigerant system from extremes of pressure. The automatic temperature control (ATC) module transmits the air conditioning (A/C) pressure, along with the compressor drive current value, to the instrument cluster on the medium speed controller area network (CAN) bus. These signals are broadcast to the engine control module (ECM) on the high speed controller area network (CAN) bus to allow it to calculate the torque being applied to the engine by the compressor.
To protect the system from extremes of pressure, the automatic temperature control (ATC) module sets the air conditioning (A/C) compressor to the minimum flow position if the pressure
- Decreases to 2.1 ± 0.2 bar (31.5 ± 3 lbf/in 2 ); the automatic temperature control (ATC) module loads the air conditioning (A/C) compressor again when the pressure increases to 2.3 ± 0.2 bar (33.4 ± 3 lbf/in 2 ).
- Increases to 31 ± 1 bar (450 ± 14.5 lbf/in 2 ); the automatic temperature control (ATC) module loads the air conditioning (A/C) compressor again when the pressure decreases to 26 ± 1 bar (377 ± 14.5 lbf/in 2 ).
Evaporator Temperature Sensor
The evaporator temperature sensor is a negative temperature coefficient (NTC) thermistor that provides the automatic temperature control (ATC) module with a temperature signal from the downstream side of the evaporator. The evaporator temperature sensor is mounted directly onto the evaporator matrix fins.
The automatic temperature control (ATC) module uses the input from the evaporator temperature sensor to control the load of the air conditioning (A/C) compressor and thus the operating temperature of the evaporator.
Humidity and Temperature Sensor
The humidity and temperature sensor is installed above the glovebox in the instrument panel. The sensor incorporates
- A negative temperature coefficient (NTC) thermistor to measure temperature.
- A capacitive sensor element to measure humidity.
- A motor driven fan to draw air through the sensor and over the sensing elements.
The humidity sensor element is built out of a film capacitor on different substrates. The dielectric is a polymer which absorbs or releases water proportional to the relative humidity of the air being drawn through the sensor, and thus changes the capacitance of the capacitor. For protection, the sensor element is contained in a nylon mesh cover.
Humidity within the passenger compartment is controlled by raising and lowering the evaporator temperature. An increase in evaporator temperature increases the moisture content of the air entering the passenger compartment. Lowering the evaporator temperature reduces the moisture content of the air entering the passenger compartment.
Ambient Air Temperature Sensor
| Item Number | Description |
|---|---|
| 1 | Left-hand (LH) door mirror |
| 2 | Ambient air temperature sensor |
The ambient air temperature sensor is a negative temperature coefficient (NTC) thermistor that provides the automatic temperature control (ATC) module with an input of external air temperature. The sensor is hard wired to the engine control module (ECM) and its signal is transmitted to the instrument cluster on the high speed controller area network (CAN) bus. The instrument cluster acts as a gateway and transmits the ambient air temperature signal to the automatic temperature control (ATC) module on the medium speed controller area network (CAN) bus. The sensor is installed in the left-hand (LH) door mirror, and is accessed by removing the mirror glass, cap and actuator.
Sunload Sensor
The sunload sensor consists of two photoelectric cells that provide the automatic temperature control (ATC) module with inputs of light intensity; one as sensed coming from the left of the vehicle and one as sensed coming from the right. The inputs are a measure of the solar heating effect on vehicle occupants, and are used by the automatic temperature control (ATC) module to adjust blower speed, temperature and distribution to improve comfort.
The sensor is installed in the speaker grill on the upper surface of the instrument panel. Power for the sensor is provided by a 5 V feed from the instrument cluster.
The sensor also contains the active anti-theft alarm indicator. Refer to Anti-Theft - Active or Anti-Theft - Active information.
Pollution Sensor (Where Fitted)
The pollution sensor allows the automatic temperature control (ATC) module to monitor the ambient air for the level of hydrocarbons and oxidized gases such as nitrous oxides, sulphur oxides and carbon monoxide. The sensor is attached to the center of the upper front crossmember.
The pollution sensor is powered by an ignition controlled voltage feed from the central junction box (CJB) and provides the automatic temperature control (ATC) module with separate signals of hydrocarbon and oxidized gas levels. With a pollution sensor fitted, the automatic temperature control (ATC) module can control the air inlet source to reduce the amount of contaminants entering the passenger compartment. This function is fully automatic, but can be overridden by manual selection of the air source using the recirculation switch on the integrated control panel.
If there is a fault with the sensor, the automatic temperature control (ATC) module disables automatic operation of the recirculation door.