Part 2 of 2
HEADLAMP POWER WASH
A power wash jet for each headlamp is located in a housing on the top surface of the front bumper. The jets are fed with fluid at high pressure from the headlamp power wash pump. A large diameter hose connects each jet to the pump. Each connection is secured with a metal clip to secure the hose due to the high pressure from the pump. Each jet directs the high-pressure fluid in a wide spray onto the headlamp lens.
OPERATION - FRONT WIPERS
The front wiper system has the following functionality:
^ Intermittent wipe and delay adjustment or rain/light sensor (if fitted)
^ Normal (slow) speed wipe
^ Fast speed wipe
^ Programme wash/wipe
^ Flick wipe
^ Headlamp power wash
^ Motor blocking protection.
Intermittent
Intermittent wiper operation is selected on the wiper control column switch, by moving the switch vertically, to the first position. The intermittent delay period is adjustable using the rotary switch on the wiper control column switch. The delay period is also subject to vehicle speed, with the selected delay period decreasing with an increase in road speed.
The rotary potentiometer selects differing resistance values for each position. The potentiometer is connected into a voltage divider circuit, with a 6.8kohm resistor located in the GEM. The power supply to the voltage divider circuit is limited to 6.5V. This reduced voltage is used by the GEM to determine the position of the rotary switch as follows:
The intermittent delay is also influenced by the road speed of the vehicle using a signal value derived from the ABS control module on the K bus. The time delay periods for the vehicle stationary and when moving at different speeds are shown in seconds in the following table:
The rotary switch positions also influence the operation of the rain/light sensor (when fitted) by adjusting its sensitivity. Refer to the following rain/light sensor operation section for details.
Normal (Slow) Speed
The normal (slow) speed continuous wiper operation is selected by moving the switch vertically to the second detente position. The wipers will operate continuously when the vehicle is moving. When the vehicle is stationary (less than 4 mph (6 km/h)), the GEM operates the wipers in the intermittent mode, using a 3 second intermittent delay period.
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 GEM operates the wipers in normal (slow) speed mode.
Rain/Light Sensor
The rain/light sensor is active when the wiper column control switch is in the intermittent position. The rain/light sensor suspends wiper operation when the area of the windscreen for the rain/light sensor is dry and operates the wipers continuously (fast or slow speeds) 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 GEM will suspend rain/light 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/light sensor can be adjusted by the driver using the intermittent rotary switch on the wiper stalk. Six 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/light sensor receives vehicle speed information from the ABS control module via the instrument pack on the K bus every 2 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
Moving either the wiper column control switch forwards or pressing the switch end button selects front wash/wipe. Both switch positions are 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 GEM also powers the wiper motor after a 0.5 second delay. The GEM monitors the wash/wipe switch operation and after the switch is released, the GEM allows 3 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 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, a signal is transmitted on the I bus to the instrument cluster to illuminate the 'WASHER FLUID LOW' message in the instrument cluster 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.
Wiper Motor Blocking Protection
The wiper park signal is also used by the GEM for blocking protection of the front wiper motor. This feature protects the motor in the event of the wiper operation being obstructed.
If the GEM does not receive the wiper park signal for a period of 16 seconds, when the wiper motor is active, the GEM removes the power supply to the motor. The motor is disabled for a period of 3 minutes or until the ignition is switched off and on again. Even after the 3 minute period has elapsed, the GEM will not automatically switch the motor on, to prevent the risk of injury. The wiper switch must be moved off and then on to reactivate the wiper motor. The blocking protection active in all wiper switch positions and can only be reset by turning the ignition off.
OPERATION - REAR WIPER
The rear wiper has the following functionality:
^ Intermittent operation
^ Adjustable intermittent wipe period
^ Continuous reverse wipe function.
Wiper Operation
The rear wiper is operated by the wiper column control switch. Pushing the switch forward to the first latching position switches on the rear wiper. Moving the switch forward again to the non-latching position operates the rear wash/wipe function.
When the rear wiper is selected on, the wiper is operated in an intermittent mode, performing 1 complete wipe cycle at regular intervals. When reverse gear is engaged the rear wiper control module receives a reverse signal from the LCM. If the rear wiper is on, the control module operates the rear wiper continuously. The continuous wipe will continue until, reverse gear is disengaged or the rear wiper is switched off.
When rear wash/wipe is selected, the control module powers the washer pump for as long as the switch is held. When the switch is released, the control module initiates 5 complete wipe cycles. The first 3 wipe cycles are each accompanied by a 0.5 second operation of the rear washer pump. The final 2 cycles are to clear the tail door window and do not have a washer pump operation. If intermittent remains selected, the rear wiper continues in intermittent mode.
Intermittent Adjustment
The intermittent interval time of the rear wiper can be adjusted by the driver to wipe at between 1 and 30 second delays. Adjustment is performed by switching the rear wiper on for a short time and then off again. The next switching on of the rear wiper determines the delay period. The time lapse between the off and the next on signal is sensed by the control module which sets this period as the requested time interval between wipes. If the next on signal is more than 30 seconds after the off signal, the control module sets the time interval to the maximum 30 seconds.
Rear Wiper Motor Blocking Protection
The rear wiper control module contains similar logic to the GEM to protect the rear wiper motor in the event of the wiper operation being obstructed.
OPERATION - HEADLAMP POWER WASHERS
The headlamp power washers are only active when the headlamps are switched on and the ignition is on. The power washers are controlled by the GEM, which limits their operation to preserve washer fluid in the reservoir.
With the ignition and lights on, headlamp power wash is activated on the first operation of the wiper column control switch in the wash/wipe position. The GEM then suspends headlamp power wash activation for the next 4 operations of the wash/wipe switch, with the headlamp power washers activated on the fifth operation of the switch.
The GEM monitors the operation of the wash/wipe switch and maintains a counter to restrict headlamp power wash operation to every fifth operation of the wash/wipe switch. The GEM also maintains a timer, which prevents a second operation of the headlamp power wash within a 3 minute period. The counter and timer are reset when the ignition is switched off.
When headlamp power wash is active, the GEM energises the power wash pump twice per cycle. The headlamp power wash pump is powered for a 0.5 second period. The GEM then initiates a 2 second delay before powering the headlamp power wash pump for a second 0.5 second period.
If the washer reservoir fluid level becomes low, the LCM, which monitors the fluid level, sends a message, via the I bus, instrument cluster and K bus, to the GEM, which suspends headlamp power wash operation to preserve the remaining washer fluid.
DIAGNOSTICS
The diagnostic socket allows the transfer of information between the GEM, the rain/light sensor and the Land Rover approved diagnostic system. The diagnostic socket is located in the fascia, in the driver's side stowage tray. The socket is secured in the fascia and protected by a hinged cover.
The rain/light sensor can store fault codes, which can be used to diagnose faults or non-function of the rain/light sensor. The faults are stored in a non-volatile memory, which retains the logged fault codes even when the power supply is disconnected. If a rain/light sensor fault prevents the sensor from operating, the GEM will control wiper operation as if a rain/light sensor is not installed in the system.
The GEM monitors all inputs and outputs relative to the wiper system and other GEM controlled functions. If a fault is detected, a code applicable to that fault is stored in a fault log. Two fault logs are provided within the GEM for internal and external faults. The GEM is capable of detecting open and short circuits and also incorrect K bus messages.
WIPERS AND WASHERS CONTROL DIAGRAM
NOTE: A = Hardwired; B = K bus; C = Diagnostic DS2 bus; K = I bus
