Compressor

Compressor

K1.8 When the ECM (C0913) receives an A/C request signal via the CAN BUS, it will energise the compressor clutch relay by providing an earth path for the relay coil (C0576) on a UB wire. A feed from fuse 9 of the engine compartment fuse box is now able to flow across the energised relay (C0578) to the compressor clutch (C0127) on an R wire.

KV6 When the ECM (C0371) receives an A/C request signal via the CAN BUS, it will energise the compressor clutch relay by providing an earth path for the relay coil (C0578) on a BR wire. A feed from fuse 9 of the engine compartment fuse box is now able to flow across the energised relay (C0575) to the compressor clutch (C0127) on an R wire.

Instrument Pack

The instrument pack (C0230) acts as a gateway, relaying CAN messages to and from different components throughout the vehicle as follows:

Pressure Sensor

The pressure sensor is located in the high pressure A/C line adjacent the compressor, and replaces the more traditional trinary pressure switch. The ECM (C0913 on K Series vehicles, C0371 on KV6 vehicles) provides a 5 V reference voltage to the pressure sensor (C1257) on a UO wire. The pressure sensor (C1257) is provided an earth path by the ECM (C0913 on K Series vehicles, C0371 on KV6 vehicles) on a PB wire.

The pressure sensor (C1257) provides the ECM (C0913 on K Series vehicles, C0371 on KV6 vehicles) a signal feed on a UG wire. The value of this signal feed is dependent upon the pressure within the A/C system. The ECM uses this feed to determine the pressure within the A/C system, enabling it to carry out the following tasks:

To provide a safety cut-out function if the pressure within the A/C system goes either too high or too low. To control the speed of the cooling and condenser fans via the cooling fan control unit. To help control engine idle speed.

Evaporator Temperature Sensor

The evaporator temperature sensor is used to ensure the evaporator doesn't freeze. The ECM (C0913 on K Series vehicles, C0371 on KV6 vehicles) provides a feed to the evaporator temperature sensor on a GO wire (GU on KV6 vehicles). The sensor is provided an earth path via the ECM (C0913 on K Series vehicles, C0371 on KV6 vehicles) on a BO wire (PB on KV6 vehicles).

NOTE: The ECM also uses the evaporator temperature sensor signal in conjunction with the pressure sensor signal to help control engine idle speed.