Part 2

Control Components

Windshield Heater
The windshield heater comprises 2 heater elements, LH (left-hand) and RH (right-hand), bonded between the glass laminations. The system is switched on by pressing the momentary switch located on the control panel. When selected, the ATC (automatic temperature control) module transmits a heating request on the high speed CAN (controller area network) bus to the CJB (central junction box). On receipt of the message, the CJB (central junction box) energizes the windshield heater relay located in the BJB (battery junction box) by providing a ground path for the relay coil. The energized relay provides a battery feed to both heater elements. After a period of 4 minutes the
ATC (automatic temperature control) module removes the request for windshield heating. The CJB (central junction box) then powers down the windshield heater by removing the ground path for the relay coil.
The ATC (automatic temperature control) module will only request windshield heater operation if the engine is running. An engine status signal is provided to the ATC (automatic temperature control) module by the ECM (engine control module) over the high speed CAN (controller area network) bus.

Rear Window Heater
The rear window heater comprises a single heater element bonded to the inner surface of the glass. The system is switched on by pressing the momentary switch located on the control panel. When selected, the ATC (automatic temperature control) module transmits a heating request on the high speed CAN (controller area network) bus to the CJB (central junction box). On receipt of the message, the CJB (central junction box) energizes the rear window heater relay by providing a ground path for the relay coil. The energized relay provides a battery feed to the heater element. After a period of 12 minutes the ATC (automatic temperature control) module removes the heating request. The CJB (central junction box) then powers down the rear window heater by removing
the ground path for the relay coil.
The ATC (automatic temperature control) module will only request rear window heater operation if the engine is running. An engine status signal is provided to the ATC (automatic temperature control) module by the ECM (engine control module) over the high speed CAN (controller area network) bus.

Exterior Mirror Heaters
The operation of the exterior mirror heaters is fully automatic and requires no input from the driver. The exterior mirror heaters are active when the ambient air temperature is below 5°C (41°F) and engine coolant temperature is below 65°C (149°F). Ambient air and engine coolant temperature values are provided by the ECM (engine control module) on the high speed CAN (controller area network) bus. On receipt of these temperature values, the CJB (central junction box) determines if exterior mirror heating is required.
The CJB (central junction box) requests exterior mirror heating by transmitting a high speed CAN (controller area network) bus message to both the drivers and passenger door modules. The door modules provide feed and ground paths to the respective exterior mirror heating elements. When ambient and engine coolant temperature rises above the values stated earlier, the CJB (central junction box) transmits a high speed CAN (controller area network) bus message to the door modules canceling the heating request.

Seat Heaters
The operation of the seat heaters is controlled by the ATC (automatic temperature control) module on receipt of a heating request from either of the seat heater momentary switches located on the control panel. The switches are mounted in the LH (left-hand) and RH (right-hand) rotary controllers. A single press of a seat heater switch will implement low level heating and illuminate a tell-tale LED (light emitting diode). A second press of the switch will implement mid-level heating and illuminate 2 tell-tale LED (light emitting diode)'s. A third press of the switch will implement high level heating and illuminate 3 tell-tale LED (light emitting diode)'s. A fourth press of the switch will turn the seat heater off.
Seat heating requests are transmitted from the ATC (automatic temperature control) module to the seat heater control modules on the LIN (local interconnect network) bus. Two seat heater control modules are fitted, one under each front seat. The seat heater control modules provide an electrical supply to the seat heater elements and a temperature sensor located in the seat cushion.
The seat heater control module provides a 5 V reference feed to the seat heater temperature sensor. The seat heater temperature sensor is an NTC (negative temperature coefficient) thermistor. By monitoring the returned voltage, the control module can calculate the temperature of the seat. If the temperature rises above the target temperature, the control module will disable operation of the heater elements.

ATC MODULE

NOTE:
The 'ECON' button has been renamed 'A/C' to prevent confusion with the Stop/Start system 'Eco' switch.





The ATC (automatic temperature control) module is mounted in the center console and is integral with the control panel. The module works in conjunction with the ECM (engine control module) to control all aspects of heating, ventilation, and A/C (air conditioning). An 18-pin electrical connector on the rear of the module provides hardwired, CAN (controller area network) bus and LIN (local interconnect network) bus connections to allow interaction with A/C (air conditioning) system components and other vehicle control modules.
Six different ATC (automatic temperature control) modules (2 single zones, 4 dual zones) are available, depending on vehicle specification. Low specification vehicles feature 3 rotary controllers and 3 top hinged momentary switches to control the quality, temperature and distribution of air into the cabin. High specification vehicles feature 3 rotary controllers, 6 top hinged momentary switches, and 2 dual function momentary switches to control the quality, temperature and distribution of air into the cabin.
In addition to the A/C (air conditioning) system, the ATC (automatic temperature control) module controls operation of:
- The seat heaters
- The rear window heater
- The windshield heater
- The exterior mirror heaters.
For more information, refer to the 'System Operation' section above.
A number of changes have been made to the logic and operation of climate control system, within a Stop/Start cycle to:
- maintain occupant comfort
- prevent windshield misting
- conserve battery power.
This has been achieved by the ATC (automatic temperature control) module monitoring and varying, as necessary various climate control functions within a Stop/Start cycle.
In some circumstances the ATC (automatic temperature control)A has the capability to inhibit an engine shutdown or initiate an engine restart within a Stop/Start cycle. This is achieved by the ATC (automatic temperature control) module communicating with the CJB (central junction box) on the medium speed CAN (controller area network). The various override functions the ATC (automatic temperature control) has in a Stop/Start cycle are discussed below:
Coolant temperature
The ATC (automatic temperature control) module will inhibit an engine shutdown or initiate an engine restart within a Stop/Start cycle if the coolant temperature falls below the calculated threshold to support the cabin temperature set by the vehicle occupants.
Windshield demisting
The variant of climate control fitted to the vehicle influences the software changes that have been made. For example, the base climate-control system does not have a humidity sensor, as used on a highline system to initiate a windshield demist. Therefore, a calculation for demisting the windshield is made using the signals from the rain sensor and ambient temperature sensor. Using the probability that windshield misting will occur if it is raining and the ambient temperature is cool, the ATC will presume a windshield demist is required and start the engine when in a Stop/Start cycle.
Evaporator temperature the main cause of windshield misting is also monitored and the high-line climate control system will periodically cool the evaporator as necessary to reduce misting during a Stop/Start cycle. The system operates the windshield demist shutter and if the evaporator is wet the shutter will remain closed for a few seconds after an engine restart until the vapor is dissipated.
If the driver selects either 'programmed defrost' or the 'windshield heater' it is assumed that a quick demist of the windshield is required. Therefore, the ATC (automatic temperature control) via the CJB (central junction box) will either: inhibit an engine shutdown or initiate an engine restart.
Heater fan speed
During an engine shutdown the ATC (automatic temperature control) monitors cabin temperature and maintains the fan speed at a level that will conserve, for as long as possible the heat in the core of the cabin heater. If the driver selects a higher fan speed and the heat cannot be maintained in the heater core, the engine will restart.
Heated rear window and heated seats
If the heated rear window or heated seats are active or activated during an engine shutdown event the power output of the relevant system will be interrupted until the engine is restarted. The tell-tale light in the relevant switch will illuminate to indicate the system is active even though the system is receiving no power. This feature is used to conserve battery power.
Fuel fired heater
The FFBH (fuel fired booster heater) and Stop/Start system will not operate simultaneously, due to low ambient temperatures being a factor in the function of both systems.

COMPRESSOR SOLENOID VALVE

GTDi









DW12C









The compressor pressure control valve is integral with the A/C (air conditioning) compressor. The operation of the control valve is self contained. The pressure control valve controls the flow of refrigerant (displacement) through the compressor depending on the demand determined by the thermal expansion valve, effectively controlling the evaporator operating temperature and cabin humidity by varying the pressure within the A/C (air conditioning) system. For additional information, refer to Air Conditioning Air Conditioning

REFRIGERANT PRESSURE SENSOR





The refrigerant pressure sensor provides the ECM (engine control module) with a pressure input from the high pressure side of the refrigerant system. The pressure sensor is located in the refrigerant line between the condenser and the thermostatic expansion valve.
The ECM (engine control module) supplies a 5 V reference feed to the pressure sensor and receives a return signal voltage, between 0 V and 5 V, related to system pressure. The ECM (engine control module) uses the signal from the sensor to protect the refrigerant system from extremes of pressure.
If the pressure within the refrigerant system exceeds the minimum or maximum pressure limits, the ECM (engine control module) will disable the A/C (air conditioning) compressor.
The ECM (engine control module) constantly sends a refrigerant system pressure signal to the ATC (automatic temperature control) module. The signal is transmitted from the ECM (engine control module) to the CJB (central junction box) over the high speed CJB (central junction box) bus. The CJB (central junction box) acts as a gateway and provides the pressure signal to the ATC (automatic temperature control) module over the medium speed CAN (controller area network) bus.
If the pressure within the refrigerant system rises above its maximum pressure limit, the ATC (automatic temperature control) module will increase the amount of re-circulated air entering the cabin. This helps lower the pressure within the refrigerant system and thus helps to avoid having to disable the A/C (air conditioning) compressor.

EVAPORATOR TEMPERATURE SENSOR





The evaporator temperature sensor is a NTC (negative temperature coefficient) thermistor. The sensor is mounted on the LH (left-hand) side of the heater casing, and measures the temperature of cooled air once it has traveled over the evaporator. The sensor receives a 5 V reference feed from the ATC (automatic temperature control) module. By monitoring the returned voltage, the ATC (automatic temperature control) module can calculate the resistance of the sensor and hence evaporator temperature.

CABIN TEMPERATURE SENSOR





The cabin temperature sensor comprises a NTC (negative temperature coefficient) thermistor and a motor. The sensor is mounted behind a grill on the drivers side of the instrument panel, adjacent the steering column.
The motor is provided an electrical feed from the ATC (automatic temperature control) module and draws cabin air in through the grill and over the thermistor. The thermistor receives a 5 V reference feed from the ATC (automatic temperature control) module. By monitoring the returned voltage, the ATC (automatic temperature control) module can calculate air temperature within the cabin.

CABIN HUMIDITY SENSOR





The cabin humidity sensor is located within the interior mirror and comprises 3 individual elements:
- A humidity sensor
- An air temperature sensor
- A windshield glass temperature sensor.

NOTE:
The cabin humidity sensor is an optional fit only.
The readings from these 3 sensors combine to reduce the risk of misting on the windshield.
The humidity sensor element is contained behind a nylon mesh cover. The sensor comprises an element made up of film capacitors on different substrates. The dielectric is a polymer which absorbs or releases water proportional to the humidity of the air being drawn through the sensor. This causes a change in the capacitance of the sensor.
Humidity within the cabin is controlled by raising or lowering the temperature of the evaporator. An increase in evaporator temperature increases the moisture content of the air in the cabin. Lowering the evaporator temperature reduces the moisture content of the air in the cabin.
The capacitance of the sensor, together with both temperature values, is provided as LIN (local interconnect network) bus messages to the ATC (automatic temperature control) module. The ATC (automatic temperature control) module uses these signals to calculate the dew point of the air at the windshield. When the temperature of the windshield glass reaches or falls below this value, misting is likely to occur. In this instance, the ATC (automatic temperature control) module will:
- raise the temperature of the air leaving the heater assembly
- adjust the position of the windshield distribution (defrost) stepper motor
- adjust the position of the air intake stepper motor
- the power windshield heater elements.

AMBIENT AIR TEMPERATURE SENSOR





The ambient air temperature sensor is a NTC (negative temperature coefficient) thermistor, and is mounted in the LH (left-hand) door mirror. The sensor receives a 5 V reference feed from the ECM (engine control module). By monitoring the returned voltage, the ECM (engine control module) can calculate the resistance of the sensor and hence ambient air temperature. The ECM (engine control module) transmits an ambient air temperature value over the high speed CAN (controller area network) bus. This value is relayed to the ATC (automatic temperature control) module by the CJB (central junction box) over the medium speed CAN (controller area network)
bus.

SUNLOAD SENSOR





The sunload sensor is mounted in the center of the instrument panel upper surface. The sensor contains a photoelectric cell, which provides the CJB (central junction box) with an input of light intensity equating to the solar heating effect on the cabin.
The solar heating value is transmitted from the CJB (central junction box) to the ATC (automatic temperature control) module over the medium speed CAN (controller area network) bus. The ATC (automatic temperature control) module compensates for the solar heating effect by adjusting blower speed, air output temperature and air distribution to maintain the required cabin temperature.

POLLUTION SENSOR





The pollution sensor allows the ATC (automatic temperature control) module to monitor intake air for the level of carbon monoxide (CO) and oxides of nitrogen (NOx). The sensor is mounted on the passenger side of the heater casing.

NOTE:
The pollution sensor is an optional fit on vehicles with a dual zone, automatic climate control system.
The pollution sensor is provided an ignition controlled feed from the BJB (battery junction box) and provides one of the following 4 signals to the ATC (automatic temperature control) module based on ambient air quality:
- Static or reduced pollution levels
- Small increase in pollution levels
- Medium increase in pollution levels
- Rapid or large increase in pollution levels.
Based on the signal from the pollution sensor, the ATC (automatic temperature control) module is able to control the intake air source to reduce the amount of contaminants entering the cabin. This function is fully automatic, but can be overridden by manual selection of the air intake source using the fresh/re-circulated air switch on the control panel.