Operation

OPERATION

General

Feed from the positive battery terminal (C0192) is supplied to fusible link 1, fusible link 5, and the main relay (C0632) on an R wire. All are located within the engine compartment fuse box.

The earth path for the main relay coil (C0578) is controlled by the Engine Control Module (ECM) (C0604) on an NG wire. The energised main relay provides a feed to fuse 4, which is also located in the engine compartment fuse box. For more details on main relay operation, refer to the Engine Management Systems – Siemens (NAS) section of the System Description and Operation Workshop manual.

Fusible link 1 is connected in series with fuse 8, fuse 9 and fusible link 2, which are also located in the engine compartment fuse box. Fuse 8 (C0576) provides a constant battery feed to the blower relay (C0153) on a GN then GW wire. Fuse 9 provides a constant battery feed to the compressor clutch relay, which is also located in the engine compartment fuse box.

Fusible link 2 (C0571) is connected to the ignition switch (C0028) by an NR wire. When the ignition switch is turned to the 'ignition' position, current flows across the switch to fuse 4 of the passenger compartment fuse box (C0588) on an SU wire. Fuse 4 (C0586) provides an ignition feed to following on G then LGS wires:

The blower motor switch (C0058). The fresh/recirculated air switch (C0750). The fresh/recirculated air motor (C0006).

A/C Master Switch

When the blower switch (C0058) is turned to position 1 or higher, it provides a feed to the A/ C master switch (C0275) on an SW wire. If A/C is requested, the switch (C0275) provides a feed to the instrument pack (C0233) on an SK wire. When the instrument pack receives an A/C request from the switch, it informs the ECM (C0331) via the CAN BUS on YN (Low) and YB (High) wires.

The A/C master switch is mounted on the centre console, and is earthed (C0275) on a B wire.

For more information on CAN BUS operation, refer to the Communication Databuses section of the System Description and Operation Workshop manual.

Compressor

When the ECM (C0331) 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 (C0575) to the compressor clutch (C0127) on an R wire.