Starting

Starting

Provided that the engine immobiliser has been disarmed, the fuel pump relay is energised by the ECM for a few seconds after the ignition is switched to position II and continuously during cranking and once the engine has started. The ECM energises the fuel pump relay by connecting an earth to the P (VVC MEMS 2J models) or BP wire (MPi MEMS 1.9 and MPi MEMS 3 models) between the fuel pump relay (C0154) and the ECM (C0159 on MPi MEMS 1.9 and VVC MEMS 2J models, C0634 on MPi MEMS 3 models).

When the engine immobiliser is disarmed, the coil of the starter relay (C0154) is earthed through the alarm ECU (C0061) on a BW wire (manual gearbox models), or on a BR wire to the park/neutral switch (C0268) and a BW wire from the park/neutral switch (C0268) to the alarm ECU (EM-CVT models). When the ignition is switched from position II to position III, the power feed from the ignition switch through fuse 19 of the satellite fuse box energises the starter relay. With the starter relay energised, the supply from fuse 1 of the under bonnet fuse box is fed from the starter relay (C0157) to the solenoid in the starter motor (C0179) on a NR wire. The solenoid earths through the starter motor fixings and energises to connect the direct feed from the battery to the starter motor. The starter motor is also earthed through the starter motor fixings.

Charging

Current flow through the ignition/no charge warning lamp and the field windings partially magnetises the rotor. When the engine is started, the magnetised rotor turns within the stator windings, generating a 3 phase alternating current (ac) and voltage that rises rapidly with rotor speed. The field diodes convert the ac into dc and generated voltage is fed back to the field windings. The fed back voltage causes an increase to the magnetic influence of the rotor, resulting in self-excitation of the rotor. The field current increases with rotor speed and thus increases generated current and voltage until the alternator is fully excited.

When the voltage applied to the alternator side of the ignition/no charge warning lamp exceeds battery voltage, the ignition/no charge warning lamp is extinguished, indicating that the alternator is developing battery charging current. A diode prevents reverse flow through the ignition/no charge warning lamp. The regulator functions as an electronic control switch on the earth side of the field coils, rapidly switching the earth circuit off and on to maintain the maximum voltage and thus the current, to safe limits.

If the battery is in a low state of charge, or current draw from electrical units causes a voltage drop, the alternator automatically charges at its maximum rate until 14 volts is reached. When the demand on the alternator falls, the current output is reduced.