Range Rover P38
ELECTRICAL
19
DESCRIPTION AND OPERATION
All front wiper functions are controlled from a stalk
switch located on the right hand side of the steering
column. The front wiper functions, with the exception
of the programmed wash wipe function, are operated
by a combination of three switches. The following
table details the switch combinations for each
function.
Function
Switch
1
Switch
2
Switch
3
Flick wipe
Closed
Open
Open
Off
Open
Open
Open
Intermittent
Open
Closed
Open
Slow
Open
Closed
Closed
Fast
Open
Open
Closed
Flick wipe
The flick wipe function is operated by pushing the
stalk vertically upwards and releasing to perform one
cycle of the front wipers. Holding the stalk in this
position will operate the wipers for as long as the
switch is held.
When the three switches are in a combination for flick
wipe operation, the BeCM output to relay 1 is earthed,
energising the relay coil. With the relay energised, a
feed from fuse 25 in the engine compartment fusebox
is supplied, via the contacts of relay 8, to the slow
speed brushes in the wiper motor. When the wiper
motor moves from the park position, the contacts of
the park switch open.
When the switch is released, the BeCM continues to
energise the coil of relay 1 to allow the wipers to move
to the park position. When the motor reaches the park
position, the park switch closes completing an earth
path to the BeCM. The BeCM senses the completed
earth path and removes the earth for the relay 1 coil,
replacing it with a 12 V output. The relay 1 coil is
de-energised and the relay contacts open, removing
the feed to the motor and stopping the wipers.
Intermittent wipe
The intermittent function is operated by pushing the
switch one position vertically downwards to the first
position. The intermittent delay can be adjusted by
rotating the thumb wheel on the top of the stalk to the
left or right to reduce or increase the delay period.
When the three switches are in a combination for
intermittent operation, the BeCM output to relay 1 is
earthed, energising the relay coil. With the relay
energised, a feed from fuse 25 in the engine
compartment fusebox is supplied, via the contacts of
relay 8, to the slow speed brushes in the wiper motor.
When the wiper motor moves from the park position,
the contacts of the park switch open.
When the wiper motor reaches the park position, the
park switch closes completing an earth path to the
BeCM. The BeCM senses the completed earth path
and removes the earth for the relay 1 coil, replacing it
with a 12 V output. The relay 1 coil is de-energised
and the relay contacts open, removing the feed to the
motor and stopping the wipers.
The BeCM then initiates a delay by passing a voltage
to the delay potentiometer and measuring the
resistance through the potentiometer. The resistances
sensed by the BeCM and the associated delays are
listed in the following table.
Delay (Seconds)
Resistance (Ohms)
2
1.9K
4
4.7K
8
9.2K
16
17.4K
32
53K
When the delay has elapsed, the BeCM will operate
the wipers for one more cycle and then reinstate the
delay period. This will continue until the intermittent
function is deselected.