Heated Front Screen (HFS)

HEATED FRONT SCREEN (HFS)

DESCRIPTION

General
The Heated Front Screen (HFS) consists of two heater elements which are embedded into the LH and RH sides of the windscreen. Two connectors at the base of the windscreen provide the power feed and an integral earth for each of the heater elements.

Operation of the HFS is controlled by the CCU and a non latching switch on the center console. The switch contains an LED which illuminates while the HFS is on. The CCU deenergises the HFS relay after approximately 5 minutes, when the switch is pressed again or if the engine stops.

OPERATION

General
Feed from the positive battery terminal (C0192) is supplied to fusible link 3 of the engine compartment fuse box (C0632) on an R wire and the Heated Front Screen (HFS) relay (C0994) on an N wire.

Fusible link 3 (C0571) provides a constant battery feed to the ignition switch (C0028) on an N wire. When the ignition switch is turned to the 'ignition' position, current flows across the switch (C0028) to fuse 8 of the passenger compartment fuse box (C0588) on a G wire. Fuse 8 provides an ignition feed to the CCU (C0593), which is mounted on the rear of the passenger compartment fuse box. The CCU (C0593) is earthed via the passenger compartment fuse box (C0587) on a B wire.

HFS Relay
The battery (C0192) provides a constant battery feed to the HFS relay coil (C0994) on an N wire. The earth path for the relay coil (C0994) is controlled by the CCU (C0429) on an SB wire.

The CCU will only provide an earth path for the HFS relay coil if all of the following are present:
^ The ignition is on.
^ The engine is running.
^ The HFS switch is pressed.

The CCU (C0592) monitors the condition of the oil pressure switch (C0187) on a WN wire. The oil pressure switch contacts are closed when there is no oil pressure. When the engine is started, the rise in oil pressure causes the switch contacts to open.