Wipers and Washers
WIPERS AND WASHERS
DESCRIPTION
General
The wipers and washers system is controlled by the Body Control Unit (BCU) on receipt of requests made by the driver or the rain sensor unit (if fitted). All wiper functions for the front and rear wipers are controlled from a multifunction wash/wipe switch assembly located on the right hand side of the steering column.
Optional equipment on Range Rover includes a rain sensor. The sensor, located below the interior rear view mirror, detects rain drops on the windscreen and automatically operates the wipers in the intermittent mode.
NOTE: The column stalk switch must be in the intermittent position for rain sensor controlled wiper operation.
The front wiper system has four stages of wiper operation with four different delay periods for intermittent wipe. The four stages are as follows:
- Flick wipe
- Intermittent
- Normal (slow) speed continuous
- Fast speed continuous.
The intermittent wiper delay periods change with the road speed, with the delay decreasing as the road speed increases. Normal continuous operation changes to intermittent operation when the vehicle is stationary. Fast speed operation changes to normal operation when the vehicle is stationary.
OPERATION
Front
Power Distribution
Feed from the positive battery terminal (C0192) is supplied to fuse 26 and fuse 53 of the passenger compartment fuse box (C0632) on an R wire. Fuse 26 (C0583) provides a constant battery feed to the wiper delay ECU (C0546) on an RW wire.
Fuse 53 (C0583) provides a constant battery feed to the ignition switch (C0028 on V8 vehicles) on an R wire. When the ignition switch is turned to the 'auxiliary' position, current flows across the switch (C0028 on V8 vehicles) to fuse 41 of the passenger compartment fuse box (C0585) on a PB wire. Fuse 41 (C0586) provides an auxiliary ignition feed to the Body Control Unit (BCU) (C0660) on a PW wire, and the rain sensor (C0961) on a PR wire.
Rain Sensor
The rain sensor (C0961) is mounted on the upper edge of the windscreen. It is provided an auxiliary ignition feed from fuse 41 of the passenger compartment fuse box (C0586) on a PR wire, and is earthed on an NB wire. The rain sensor (C0961) provides information to the BCU (C0660) via the K bus on a WRY wire. This information is used by the BCU to determine optimum wiper operation for the prevailing conditions.
Steering Wheel Switch
The BCU (C0660) provides feeds to the steering wheel switches (C0278) on BW and BU wires. The steering wheel switch (�20278) is earthed on an NB wire. The BCU determines which function has been selected by the earth paths that are created by the switch. If slow wipe is selected, current on the BW wire flows across the switch to earth. If fast wipe is selected, current on both the BW and BU wires flows across the switch to earth. If intermittent wipe is selected, current on the BU wire flows across the switch to earth.
The steering wheel switch also contains a rotary potentiometer to control the intermittent wipe function. The intermittent wipe setting is interpreted by the BCU (C0661) from the feed returned from the switch (C0278) on a BG wire.
When the BCU (C0661) senses that wiper operation is required, it provides a feed to the wiper delay ECU (C0546) on an NU wire. The wiper delay ECU (C0546) is earthed on an N wire and provides two feeds to the wiper motor (C0546) on BG and BN wires.
Washer
If the steering wheel switch is pulled towards the driver, current flows from the BCU (C0660) to the steering wheel switch (C0278) on an NP wire, and then to earth on an NB wire. Sensing this earth, the BCU (C0662) provides a feed to the washer pump motor (C0008) on a B wire. Current flows across the washer pump motor (C0008) to earth on an N wire. The BCU powers the washer pump motor for as long as the switch is held in position, and also powers the wipers at slow speed.
Rear
Power Distribution
Feed from the positive battery terminal (C0192) is supplied to fuse 27, fuse 53, and fusible link 5 of the passenger compartment fuse box (C0632) on an R wire. Fuse 27 (C0585) provides a constant battery feed to the BCU (C0662) on an RU wire. Fusible link 5 (C0588) is connected tn fuse 10 of the rear fuse box (C2024) nn an R wire. Fuse 10 (C2021) provides a constant battery feed to the rear screen wiper ECU (C0388) on an RW wire.
Fuse 53 of the passenger compartment fuse box (C0583) is connected to the ignition switch (C0028 on V8 vehicles) by an R wire. When the ignition switch is turned to the 'auxiliary' position, current flows across the switch (C0028 on V8 vehicles) to fuse 41 of the passenger compartment fuse box (C0585) on a PB wire. Fuse 41 (C0586) provides an auxiliary ignition feed to the rear screen wiper ECU (C0835) on a PR wire. The ECU is earthed on an N (C0388) and an NB (C0835) wire.
Rear Wiper ECU
Operation of the rear wiper and washer system is controlled by the rear wiper ECU, which is integral with the motor assembly. The ECU (C0835) monitors the condition of the steering wheel switch (C0278) by providing feeds on BW and BU wires. If a request is made for rear wiper or washer operation, an earth path is created on an NB wire.
The rear wiper ECU (C0835) receives a 'reverse gear selected' signal from the Light Check Module (LCM) (C2040) on a UY wire. When the rear wiper ECU receives this feed it powers the rear wiper motor.
Washer
When the rear wiper ECU receives a washer request from the steering wheel switch, it provides a feed to the rear washer pump (C0021) on a BR wire. Current flows across the pump motor (C0021) to earth on an N wire.