Description

Control Components

NOTE:
A = Hardwired; N = Medium speed CAN (controller area network) bus; O = LIN (local interconnect network) bus; P = Media orientated system transport (MOST) ring.









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 ATC (automatic temperature control) module determines the required position of the recirculation door from its 'comfort' algorithm and, if fitted, the pollution sensor.
The ATC (automatic temperature control) module provides analogue signals to the air inlet servo motor along a hardwired connection. A potentiometer in the motor supplies the ATC (automatic temperature control) 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 ATC (automatic temperature control) module using LIN (local interconnect network) bus messages.
The ATC (automatic temperature control) 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 ATC (automatic temperature control) 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 ATC (automatic temperature control) 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 A/C (air conditioning) 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 ATC (automatic temperature control) 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 ATC (automatic temperature control) module determines the blower speed required from a comfort algorithm. When the system is in the manual mode, the ATC (automatic temperature control) 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 ATC (automatic temperature control) 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 ATC (automatic temperature control) module using LIN (local interconnect network) bus messages.
When the A/C (air conditioning) system is in automatic mode, the ATC (automatic temperature control) 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 A/C (air conditioning) is selected the ATC (automatic temperature control) module maintains the evaporator at an operating temperature that varies with the passenger compartment cooling requirements. If the requirement for cooled air decreases, the ATC (automatic temperature control) module raises the evaporator operating temperature by reducing the flow of refrigerant provided by the A/C (air conditioning) compressor. The ATC (automatic temperature control) module closely controls the rate of temperature increase to avoid introducing moisture into the passenger compartment.
If the requirement for cooled air increases, the ATC (automatic temperature control) module lowers the evaporator operating temperature by increasing the flow of refrigerant provided by the A/C (air conditioning) compressor.
When A/C (air conditioning) is off, the compressor current signal supplied by the ATC (automatic temperature control) module holds the A/C (air conditioning) compressor solenoid valve in the minimum flow position, effectively switching off the A/C (air conditioning) function.
The ATC (automatic temperature control) 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 A/C (air conditioning) compressor is maintained at its minimum stroke. This avoids depletion of the lubricant from the A/C (air conditioning) compressor.

A/C Compressor Torque
The ATC (automatic temperature control) module transmits refrigerant pressure and A/C (air conditioning) compressor current values to the ECM (engine control module) over the medium speed then high speed CAN (controller area network) bus, using the CJB (central junction box) as a gateway. The ECM (engine control module) uses these values to calculate the torque being used to drive the A/C (air conditioning) compressor. The ECM (engine control module) compares the calculated value with its allowable value and if necessary forces the ATC (automatic temperature control) module to inhibit the A/C (air conditioning) compressor by transmitting the 'ACClutchInhibit' CAN (controller area network) message. This forces the ATC (automatic temperature control) module to reduce the drive current to the A/C (air conditioning) compressor solenoid valve, which reduces refrigerant flow. This in turn reduces the torque required to drive the A/C (air conditioning) compressor.
By reducing the maximum A/C (air conditioning) compressor torque, the ECM (engine control module) is able to reduce the load on the engine when it needs to maintain vehicle performance or cooling system integrity.

Cooling Fan Control
The ATC (automatic temperature control) 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 ECM (engine control module) on the medium speed CAN (controller area network) bus. The ECM (engine control module) 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 ATC (automatic temperature control) module instigates the programmed defrost function. When selected, the ATC (automatic temperature control) module configures the system as follows:
- Automatic mode off.
- A/C (air conditioning) 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 ATC (automatic temperature control) module controls operation of the rear window heater using a relay in the RJB (rear junction box). When rear window heater operation is required, the ATC (automatic temperature control) module broadcasts a message to the RJB (rear junction box) on the medium speed CAN (controller area network) bus. On receipt of the message, the RJB (rear junction box) 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 LED (light emitting diode) 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 LED (light emitting diode) 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 LED (light emitting diode) 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 ATC (automatic temperature control) module controls operation of the windshield heater using two relays in the EJB (engine junction box). When windshield heater operation is required, the ATC (automatic temperature control) module broadcasts a message to the CJB (central junction box) on the medium speed CAN (controller area network) bus. On receipt of the message, the CJB (central junction box) 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 LED (light emitting diode) 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 LED (light emitting diode) 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 LED (light emitting diode) 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 ATC (automatic temperature control) module broadcasts an exterior mirror heating request to the door modules over the medium speed CAN (controller area network) 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 ATC (automatic temperature control) module. When the ATC (automatic temperature control) module receives a heating request from the TSD, it broadcasts a message to the CJB (central junction box) over the medium speed CAN (controller area network) bus. The CJB (central junction box) 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 ATC (automatic temperature control) module monitors seat temperature using a temperature sensor located in each seat cushion. The CJB (central junction box) provides the temperature sensors with a 5 V
supply. The level of the returned voltage back to the CJB (central junction box) is proportional to the seat temperature. The value of the return signal is broadcast to the ATC (automatic temperature control) module, over the medium speed CAN (controller area network) bus, which allows it to control the seat temperature to the required level. The ATC (automatic temperature control) 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 CJB (central junction box) on receipt of a request from the ATC (automatic temperature control) module over the medium speed CAN (controller area network) bus. Temperature control for the heater element is provided by the steering wheel heater control module which receives a temperature feedback signal from a NTC (negative temperature coefficient) thermistor located within the steering wheel.

ATC Module





The ATC (automatic temperature control) module is mounted on the outboard end of the air inlet duct, behind the front passenger side of the instrument panel. The ATC (automatic temperature control) module processes inputs from the TSD, the switches on the integrated control panel and the system sensors. In response to these inputs, the ATC (automatic temperature control) module outputs control signals to the A/C (air conditioning) system and the heating and ventilation system.
Two electrical connectors provide the interface between the ATC (automatic temperature control) module and the vehicle wiring. The ATC (automatic temperature control) module uses hardwired inputs from the system sensors, the LIN (local interconnect network) bus to communicate with the stepper motors and the medium speed CAN (controller area network) bus to communicate with other control modules on the vehicle.

A/C Compressor Solenoid Valve
The A/C (air conditioning) compressor solenoid valve is integral with the A/C (air conditioning) compressor. Operation of the solenoid valve is controlled by the ATC (automatic temperature control) module using a hardwired drive current of differing values. By controlling the flow of refrigerant through the compressor, the solenoid valve can control the A/C (air conditioning) system pressure and the evaporator operating temperature.

Refrigerant Pressure Sensor





The refrigerant pressure sensor provides the ATC (automatic temperature control) 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 ATC (automatic temperature control) 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 ATC (automatic temperature control) module uses the signal from the pressure sensor to protect the refrigerant system from extremes of pressure. The ATC (automatic temperature control) module transmits the A/C (air conditioning) pressure, along with the compressor drive current value, to the instrument cluster on the medium speed CAN (controller area network) bus. These signals are broadcast to the ECM (engine control module) on the high speed CAN (controller area network) 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 ATC (automatic temperature control) module sets the A/C (air conditioning) compressor to the minimum flow position if the pressure:
- Decreases to 2.1 ± 0.2 bar (31.5 ± 3 lbf/in2); the ATC (automatic temperature control) module loads the A/C (air conditioning) compressor again when the pressure increases to 2.3 ± 0.2 bar (33.4 ± 3 lbf/in2).
- Increases to 31 ± 1 bar (450 ± 14.5 lbf/in2); the ATC (automatic temperature control) module loads the A/C (air conditioning) compressor again when the pressure decreases to 26 ± 1 bar (377 ± 14.5 lbf/in2).

Evaporator Temperature Sensor





The evaporator temperature sensor is a NTC (negative temperature coefficient) thermistor that provides the ATC (automatic temperature control) 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 ATC (automatic temperature control) module uses the input from the evaporator temperature sensor to control the load of the A/C (air conditioning) 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 NTC (negative temperature coefficient) 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









The ambient air temperature sensor is a NTC (negative temperature coefficient) thermistor that provides the ATC (automatic temperature control) module with an input of external air temperature. The sensor is hard wired to the ECM (engine control module) and its signal is transmitted to the instrument cluster on the high speed CAN (controller area network) bus. The instrument cluster acts as a gateway and transmits the ambient air temperature signal to the ATC (automatic temperature control) module on the medium speed CAN (controller area network) bus. The sensor is installed in the LH (left-hand) 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 ATC (automatic temperature control) 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 ATC (automatic temperature control) 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. For additional information, refer to Anti-Theft - Active

Pollution Sensor (Where Fitted)





The pollution sensor allows the ATC (automatic temperature control) 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 CJB (central junction box) and provides the ATC (automatic temperature control) module with separate signals of hydrocarbon and oxidized gas levels. With a pollution sensor fitted, the ATC (automatic temperature control) 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 ATC (automatic temperature control) module disables automatic operation of the recirculation door.