Air Conditioning - Low Line

Air Conditioning - Low Line

OPERATION

Power Distribution
Feed from the positive battery terminal (C0192) is supplied to fusible link 12E and fusible link 17E (C0632) on an R wire. Both are located in the Battery Junction Box (BJB). Fusible link 12E provides a constant battery feed to the blower relay, which is also located in the BJB. The ground path for the relay coil (C0570) is controlled by the ATCM (C1629) on an LGW wire.

Fusible link 17E (C0570) is connected to fuse 51P of the Central Junction Box (CJB) (C0583) on an NR wire. Fuse 51P (C0582) provides a constant battery feed to the ATCM (C2655) on a GP wire. The ATCM (C2655) is provided a ground path on a B wire.

ATCM
In order to control the low line air conditioning system, the ATCM receives inputs from the following:

Refrigerant Pressure Sensor
The refrigerant pressure sensor (C1465) is provided a 5 V reference feed by the ATCM (C1629) on an RG wire, and a ground path on a BG wire. By measuring the value of the signal returned from the sensor on a UN wire, the ATCM can determine the pressure within the high pressure side of the air conditioning system.

Evaporator Temperature Sensor
The evaporator temperature sensor (C0417) is provided a feed by the ATCM (C1630) on an NB wire and a ground path on a P wire. The temperature within the evaporator is controlled by the ATCM via the refrigerant solenoid valve located within the A/C compressor.

Ambient Air Temperature Sensor
Readings of ambient air temperature are used to control a number of features, including the heated windshield, heated door mirrors and engine cold climate start up.

The ATCM (C1629) provides a feed to the ambient air temperature sensor (C0412) on a YN wire and a ground path on a BG wire.

Refrigerant Solenoid Valve
The refrigerant solenoid valve is located within the air conditioning compressor. By controlling the flow of refrigerant through the compressor, the valve can control the pressure within the air conditioning system and evaporator operating temperature.

Operation of the refrigerant solenoid valve is controlled by the ATCM. The ATCM (C1629) provides a Pulse Width Modulated (PWM) signal to the refrigerant solenoid valve (C0127 on TdV6 vehicles, C0182 on V6 vehicles, C0128 on V8 vehicles) on an RU wire (RU then W on TdV6 vehicles). The ATCM provides a ground path for the valve on a BU wire (S then BU on TdV6 vehicles). By varying the duty cycle of the PWM signal, the ATCM controls operation of the refrigerant solenoid valve.

Blower Motor
Operation of the blower motor is controlled by the ATCM via the blower motor control module and the blower relay.

When blower motor operation is required, the ATCM (C1629) provides a ground path for the blower relay coil (C0570) on an LGW wire. The energised relay (C0570) provides a battery feed to the blower motor (C0056) on an NR then W wire.

To control the speed of the blower motor, the ATCM (C1630) provides a PWM signal to the blower motor control module (C2281) on an LGB wire. The blower motor control module regulates the voltage flow across the motor in relation to the PWM signal. The control module is connected to the motor by a B wire, and is provided a ground path on an R then B wire.

The ATCM (C1630) provides a second feed to the blower motor control module on a G wire. This feed is used by the ATCM to confirm the speed of the blower motor.

Control Door Motors

Intake Air Motor
The intake air motor is used to switch the intake air source between fresh air and re-circulated air. To move the door to the fresh air position, the ATCM (C1630) provides a feed to the motor (C0419) on an RW wire. Current flows through the motor windings and back to the ATCM on a GB wire. To move the door to the re-circulated air position, the ATCM reverses the supply to the motor. A feed is provided on a GB wire, and a ground path via an RW wire.

The ATCM monitors the position of the motor by providing a 5 V reference feed to the position sensor (C0419) on an N wire. A ground path is provided for the sensor via the ATCM (C1630) on a P wire. By measuring the voltage returned on a YB wire, the ATCM can determine the position of the motor.

Air Distribution Motors
The ATCM (C1630) controls operation of the air distribution motors as follows:
^ A feed is provided to the motor assemblies on GY wires.
^ A ground path is provided to the motor assemblies on O wires.
^ A Local Interconnect Network (LIN) bus connection is provided to the motor assemblies on RY wires.

The LIN bus is used by the ATCM to control the position of each air distribution motor. The ATCM transmits a 'required position' message to the control units located within each motor assembly. The control units interpret this message and control operation of the motors accordingly.