Range Rover P38
ELECTRICAL
21
DESCRIPTION AND OPERATION
Speed dependant wipers (From 99MY)
Vehicles from 99MY can have a programmed speed
dependant wiper function. When this function is active
the following changes over normal wiper operation will
occur when the vehicle speed is reduced to 2 mph
(3.2 km/h) or less with a front wiper function active.
If the wipers are operating at fast speed, they will
change to slow speed when the vehicle stops.
If the wipers are operating at slow speed, they will
change to intermittent operation with a fixed delay of 2
seconds. The delay is irrespective of delay
potentiometer position.
If the wipers are operating on intermittent operation,
they will continue to operate intermittently, but the
selected delay time will be doubled.
When the vehicle speed increases to 3 mph
(4.8 km/h) or more, the wipers will operate one
complete cycle and continue as previously selected.
When the vehicle is stationary, if the wiper switch is
moved the selected function will operate normally.
Headlamp Wash/Wipe
When the headlamps are switched on and the
programmed wash/wipe switch is pressed, the
headlamp wash/wipe will operate on the first and
every alternate operation of the wash/wipe switch.
The headlamp wash/wipe motor will operate for two
seconds, irrespective of how long the switch is
depressed. If the screen wash fluid level is low the
headlamp wash/wipe function is disabled by the
BeCM.
When the BeCM detects the correct conditions for
headlamp wash wipe operation, a 12 V output to relay
11 in the engine compartment fusebox is earthed,
energising the relay coil and closing the relay
contacts. A feed from fuse 38 in the engine
compartment fusebox passes through the relay
contacts and powers the LH and RH headlamp wiper
motors and the headlamp washer pump motor.
After two seconds, the BeCM removes the earth path
for the relay 11 coil, replacing it with a 12 V output.
The relay 11 coil is de-energised and the relay
contacts open, removing the feed to the headlamp
motors and washer pump. The headlamp wiper
motors continue to operate on a feed from fuse 38,
until the RH motor park switch connects the feed to
earth, stopping the motors and the washer pump.
Rear Wipers
A single rear wiper is operated direct from a motor
located in the tail door. The rear wiper and washer will
only operate with the ignition in position I or II. If the
ignition is moved to position 0 (off) when the wiper is
operating, the wiper will continue to operate until it
reaches the park position.
All rear wiper functions are controlled from a stalk
switch located on the right hand side of the steering
column.
Intermittent wipe
When the rear wiper switch is moved to the on
position, the BeCM detects a completed earth path
through the switch. The BeCM then provides a 12 V
output direct to the rear wiper motor. The motor will
operate for two complete cycles until the BeCM
senses a second operation of the motor park switch.
When the motor is operating, the park switch is closed
completing an earth path to the BeCM. When the
motor reaches the park position, the switch opens
removing the earth path and signals the BeCM that
the wiper is in the park position. The BeCM then
connects the output to the rear wiper motor to earth,
stopping the motor.
The functionality of the rear wiper is dependant on the
selected front wiper function.