Compressor

Compressor

When compressor operation is required, the ATC ECU (C1629) sends a message to the Engine Control Module (ECM) via the K bus on a WRY wire. Provided there are no engine management constraints, the ECM (C0331) responds by increasing throttle angle and fuelling and returns a signal granting operation of the compressor to the ATC ECU (C1629) on a BG wire. The ATC ECU (C1630) then provides a feed to the compressor clutch (C0182) on a BS wire.

For more details of compressor operation, refer to the Air Conditioning section of the System Description and Operation Workshop manual.

Refrigerant Pressure Sensor

The refrigerant pressure sensor is located in the refrigerant line between the condenser and the thermostatic expansion valve. It provides the ATC ECU with a pressure input from the high pressure side of the refrigerant system. The ATC ECU (C1629) provides a 5 V reference feed to the pressure sensor (C1610) on a GY wire. The pressure sensor (C1610) returns a signal voltage of between 0 V and 5 V, depending upon system pressure, to the ATC ECU (C1629) on a BS wire. The ATC ECU (C1629) provides an earth path for the pressure sensor (C1610) on an NB wire.

Evaporator Temperature Sensor

The evaporator temperature sensor is a Negative Temperature Coefficient (NTC) sensor. The ATC ECU (C0923) provides a feed to the evaporator temperature sensor (C0417) on an NB wire. By measuring the voltage returned on a YB wire, the ATC ECU (C0923) can determine evaporator temperature.

Blower Motor

Operation of the blower motor is controlled by the ATC ECU via the blower motor control unit. To control blower motor speed, the ATC ECU (C0923) provides a stepped voltage of between 0 V and 8 V to the control unit (C2281) on a UR wire. This is used by the control unit to regulate the supply voltage from maxi fuse 64 of the passenger compartment fuse box to the blower motor (C0056) on BG and RG wires.

The blower motor control unit (C2281) is earthed on an N wire.

Heater Coolant Temperature Sensor

The heater coolant temperature sensor is a Negative Temperature Coefficient (NTC) sensor. The ATC ECU (C0923) provides a feed to the temperature sensor (C0416) on an NB wire. By measuring the voltage returned on the YR wire, the ATC ECU (C0923) can determine the temperature of the air exiting the heater matrix.