L322 Range Rover System Description and Operation
WIPERS AND WASHERS
DESCRIPTION AND OPERATION
84-19
Fast Speed
The fast speed continuous wiper operation is selected by moving the switch vertically to the third detente position.
The wipers will operate continuously at fast speed when the vehicle is moving. When the vehicle is stationary (less
than 4 mph (6 km/h)), the BCU operates the wipers in normal (slow) speed mode
Rain Sensor
The rain sensor is active when the wiper column control switch is in the intermittent position. The rain sensor suspends
wiper operation when the area of the windscreen for the rain sensor is dry and operates the wipers continuously when
the windscreen is subject to heavy rainfall.
If the ignition is switched off and the wiper column control switch remains in the intermittent position, the BCU will
suspend rain sensor operation until intermittent operation is reselected, an adjustment of the rotary switch is made or
programmed wash/wipe is selected.
The sensitivity of the rain sensor can be adjusted by the driver using the intermittent rotary switch on the wiper stalk.
Four sensitivity levels of the sensor can be selected which has the effect of increasing or decreasing the wiper delay
period, allow driver adjustment for the prevailing conditions. When several continuous wipe cycles have taken place,
the sensor will maintain the continuous operation to avoid switching back to intermittent from a continuous wipe and
back again.
The rain sensor receives vehicle speed information from the ABS ECU via the instrument pack on the K bus every
two seconds. The sensor increases the sensitivity as the speed increases to optimise wiper operation. When the
vehicle speed is reduced to less than 5 mph (8 km/h), the sensitivity is automatically reduced. Below this speed the
wipers will only operate continuously in very heavy rain.
Wash/Wipe
Wash/wipe is selected by moving the wiper column control switch rearwards. This switch position is non-latching and
the windscreen washer pump is operated for as long as the switch is active. If the switch is only momentarily operated
(less than 300 ms), only the washer pump operates. If the switch is activated for more than 300 ms, the BCU also
powers the wiper motor after a 0.5 second delay. The BCU monitors the wash/wipe switch operation and after the
switch is released, the BCU allows three full wipe cycles to clear the screen.
Reservoir Level Sensor
The sensor cannot determine the precise amount of fluid in the reservoir, but can detect when the fluid level has fallen
below a certain point. When the fluid level is low, the magnetic float closes the sensor contacts, completing a circuit
through the sensor. This completed circuit is sensed by the Light Check Module (LCM), to which the sensor is directly
connected.
The fluid level sensor is monitored continuously by the LCM. The LCM checks the fluid level sensor when the ignition
is switched on to give the driver an early warning of the low fluid level. The LCM then monitors the sensor value over
a 25 second period when the ignition is on to prevent invalid messages due to fluid 'sloshing' in the reservoir.
When the LCM determines a low fluid level signal, a telegram is transmitted on the I bus to the instrument pack to
illuminate the “WASHER FLUID LOW” message in the instrument pack message centre. The first illumination of this
message is accompanied by a 'gong' sound to alert the driver to the low fluid level.
Heated Windscreen Washer Jets
The heated washer jets are controlled by the ATC system and a heated washer jet relay in the passenger
compartment fusebox. The ATC receives ambient temperature from the instrument pack on the K bus.
When the ignition is switched on and the ATC system detects an ambient temperature of less than 3
°
C (37
°
F), the
ATC system completes an earth path for the coil of the heated washer jet relay. This allows battery voltage to pass
through the relay contacts and operate the heater elements. The ATC maintains the power to the heater elements for
as long as the ignition remains on or the ambient temperature remains below 6
°
C (42
°
F). If the ambient temperature
increases to 6
°
C (42
°
F) or above, the ATC system removes the earth for the relay coil, de-energising the heater
elements.
The ATC system will also prevent heated washer jet operation if the battery voltage falls to below 11.4V. This is to
relieve loads on the battery and alternator when electrical loads are high. Heated washer jet operation will be resumed
when the battery voltage exceeds 12.2V.
