Wipers and Washers - Description & Operation Land Rover Range Rover L322

Scheme 16

Scheme 17

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.

The wiper and washer system comprises

1. Front and rear wiper motors
2. A front wiper linkage
3. Two front and one rear wiper arms and blades
4. Two front washer jets and one rear washer jet (incorporated with rear wiper arm)
5. A washer reservoir and three pumps
6. A wash/wipe control column switch.

Other items are added to enhance the wiper system

1. Heated front washer jets
2. Headlamp wash/wipe system
3. A rain sensor for automatic wiper control.

The wiper system can be optionally equipped with 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. The column stalk switch must be in the intermittent position for rain sensor controlled wiper operation. On vehicles from 2005MY the rain sensor is replaced by a combined rain/light sensor which controls the automatic wiper functions and also the automatic lighting functions.

The front wiper system has four wiper stages of operation and four intermittent wiper delay periods. The four wiper stages are as follows

1. Flick wipe
2. Intermittent
3. Normal (slow) speed continuous
4. Fast speed continuous.

The intermittent, normal and fast speeds are affected by road speed. The intermittent wiper delay periods change with the road speed, with the delay decreasing as the road speed increases. The normal continuous operation changes to intermittent operation when the vehicle is stationary. The fast speed operation changes to normal operation when the vehicle is stationary.

The wiper and washers operate with the ignition switch in positions I or II (aux or ign). Wiper functions are suspended during engine cranking to reduce battery power consumption under high load conditions.

*** Description ***

Diagnostic information for the wiper system is available and can be retrieved using T4.

Scheme 18

The wiper control column switch is located on the right hand side of the steering column and controls all front and rear wiper functions.

Moving the switch up one position selects intermittent front wiper operation. The rotary potentiometer on the stalk selects one of four delay periods. When a rain sensor is incorporated into the system, the intermittent position also initiates wiper operation controlled by the rain sensor. The sensitivity of the rain sensor can be adjusted by rotating the rotary potentiometer to one of the four positions. Moving the switch up one further position selects normal (slow) continuous wiper operation. Moving the switch up to the last position selects fast continuous wiper operation.

Moving the switch down selects the flick wipe function. The front wipers will operate at normal speed for as long as the flick wipe switch position is operated and will stop at the park position when the switch is released.

Moving the switch rearwards, towards the driver, selects the programmed front wash/wipe function. The windscreen washer pump will operate for as long as the switch is held. A short operation operates the pump momentarily and the wipers complete three full cycles before stopping. When headlamp wash/wipe is fitted, the headlamp washers and wipers will operate if programmed wash/wipe is selected and the headlamps are on. The wash/wipe function can also be selected by depressing the button on the end of the stalk.

Moving the switch forwards to the first switch position selects the rear wiper on. The rear wiper will complete one full cycle and will then operate on an intermittent function until selected off. The intermittent delay between wipes can be adjusted by selecting the wiper on, then off and then on again. Moving the switch forward to the second position selects the programmed rear wash/wipe function. The wiper completes five full cycle with three automatic, short operations of the rear washer pump. The rear wiper then operates in the rear wiper on mode until selected off.

The rear wiper also operates continuously if reverse gear is selected and the front wipers are on.

The wiper control column switch comprises 8 switch positions and the intermittent rotary control. The switch positions each complete a combination of earth paths to three connections on the BCU. The BCU interprets the selected combination of switches and operates the respective function accordingly.

Front Wipers

The front wiper system comprises

1. Wiper motor and linkage assembly
2. Washer reservoir and pumps
3. Wiper arms and blades.

Scheme 19

The wiper linkage and motor assembly are available as separate components. The wiper linkage differs between LH and RH drive models. The wiper motor is common to LH and RH drive models.

The assembly is located below the plenum grill in the engine compartment and is secured with bushes, sleeves and bolts. The rubber bushes isolate the assembly from the body mountings.

The linkage assembly comprises a main tube, with a pivot housing at each end. A bracket is attached, offset along the tube length, which locates the motor assembly. A motor crank is positively attached to the motor output shaft. A link rod is connected to the motor crank and is connected at the opposite end to the RH pivot housing, via a crank. The RH link rod has a pivot attachment for the LH link rod, which is connected at its opposite end to the RH pivot housing, via a second crank.

The motor crank converts rotary motion from the motor output shaft into linear movement of the link rods. The cranks, connected between the each link rod and pivot housing, convert the linear motion back to rotary motion of the pivot housing. This rotary motion is passed to the wiper arms and blades causing the blades to wipe an arc across the windscreen.

Wiper Motor

The motor assembly comprises a dc motor which drives a gear wheel via a worm drive attached to the motor spindle. The gear wheel has a central spigot which provides the attachment point for the motor crank.

The motor is connected electrically by a four pin connector. The connector supplies two battery voltage feeds to the motor. The motor has three sets of brushes with one brush connected to ground. One feed is direct to the motor brush opposite the ground brush and operates the motor at normal (slow) speed. The second feed is connected to a motor brush which is offset from the ground brush and operates the motor at fast speed. With the power supplied through this brush, the current flows through fewer coil windings. This results in a lower resistance to the current flow to the ground brush and gives a higher motor rotational speed.

Output control of the wiper motor is through a double contact relay. The relay is located in the engine compartment, adjacent to the transfer box ECU, behind the battery. The relay is a tan color for identification.

The motor has an internal track which signals the BCU when the wipers have reached the park position. The park signal is an open circuit when the wipers are in the park position. When the wipers are switched off and the BCU receives the park position signal from the motor, the BCU shorts the motor via a relay bridge circuit. This short circuit has the effect of applying a brake to the motor, giving precise positioning of the wiper blades in the park position.

Scheme 20

The wiper arms are positively located on tapered splines on the wiper linkage spindles. The arm is located on a curved wiper angle adjuster, which mates with the curved underside of the arm attachment. A curved slot in the arm attachment locates an adjustment shim and the three components are retained under compression on the spindle spline by a self locking nut.

The wiper angle adjuster and the angle adjust shim allow the approach angle of the wiper blade to be finely adjusted to its optimum wiping angle. The adjustment allows the approach angle of the blade to adjusted to 2° on each side of the spindle axis. This adjustment provides precise adjustment of the blade approach angle for maximum wiper performance. The wiper angle adjuster is pressed onto the spindle and requires a tool for removal. Once removed, the wiper angle adjuster must be discarded and new one fitted on re-assembly.

The wiper arm has a pivot point, midway between the spindle attachment and the blade. Two tension springs are connected to the wiper arm on each side of the pivot point and apply pressure to maintain the wiper blade in contact with the windscreen.

The wiper blades are attached to the wiper arms with clips that allow the blade to pivot. Each blade comprises a number of levers and yokes to which the rubber wiper blade is attached. The levers and yokes ensure that the pressure applied by the arm tension spring is distributed evenly along the full length of the blade and also allow the blade to adjust to the curvature and contour of the windscreen. The drivers side blade is fitted with an airfoil which presses the blade onto the windscreen at high speed, improving the wiper performance.

Scheme 21

The windscreen washer system comprises a reservoir, a washer pump, two washer jets and hoses.

The plastic, molded reservoir is located in the LH wheel arch, behind the liner and has a capacity of 8.8 pints (5 liters). It is secured to the body and front panel with bolts and washers. A boss on the reservoir locates in a slot in the front panel and provides additional support.

The reservoir has three recessed holes on its rear face which provide location for the front, rear and headlamp washer pumps. The pumps are push fitted into grommets which seal the pumps in their locations. A hole in the top of the reservoir allows for the fitment of a flexible filler tube. The hose is routed into the left hand side of the engine compartment and is sealed with a rubber cap. A breather hose is fitted into an elbow on the top of the reservoir and is routed alongside the filler and secured in a clip near the filler cap in the engine compartment.

A hole in the base of the reservoir provides the location for the fluid level sensor. The hole provides access to an internal tube inside the reservoir, into which the sensor is fitted. The sensor has two pegs which positively locate the sensor in the reservoir when turned through 90°.

The sensor reacts to the influence of a magnetic field. A float, with integral magnet, is located around the tube, inside the reservoir. The sensor has two contacts inside a glass tube, which are normally open. When the fluid level reduces, the magnetic float moves down the tube. When the magnet reaches the sensor contacts, the magnetic field closes the contacts. This completed circuit is sensed by the LCM which displays the low fluid level message in the instrument pack.

Heated Windscreen Washer Jets

Two windscreen washer jets are located in the rear trim panel on the bonnet outer surface. The washer fluid feed hose from the front screen pump is connected to a T piece connector located between the two jets. Two short lengths of hose connect the jets to the V piece. Each jet contains a non-return valve (NRV) to prevent washer fluid draining back to the reservoir and also to limit the amount of washer fluid which can be forced by gravity from the jet during cornering.

Each washer jet has two ball nozzles which can rotate in their housings to obtain the optimum fluid application onto the windscreen. Each washer jet contains a heater element which prevents the fluid freezing in the nozzles in very cold conditions. The jet heater elements are controlled by the Automatic Temperature Control (ATC) system, which energizes the heater elements when the ambient temperature falls below a predetermined temperature.

Wiper Blade Heating

The lower, black, portion of the windscreen contains six heating elements which run from one side of the screen to the other. These elements are designed to heat the area of the windscreen where the wiper blades rest to prevent freezing in cold conditions.

The blade heating elements are controlled by the ATC system, which energizes the blade heating elements when the ambient temperature falls below a predetermined temperature. The operation of the blade heating elements is activated simultaneously with the heated washer jets.

Scheme 22

Scheme 23

The rain sensor is located at the upper edge of the windscreen, behind the interior rear view mirror. The sensor is mounted on an optical unit which is heat bonded to the inner surface of the windscreen during manufacture. If damage occurs to the optical unit or the windscreen, then a new windscreen will be required and fitment can only be performed by an authorized Land Rover dealer.

The rain sensor unit attaches to the optical unit via four clips which latch onto formed tags on the optical unit. Positive retention is achieved by two retaining clips which force the clips onto the tags. The retaining clips must be withdrawn to facilitate sensor removal.

The sensor provides information to the BCU, via the K bus, for the optimum wiper operation for the prevailing conditions to maintain the screen in a clear condition at all times. The rain sensor is an optical unit which operates on an infrared waveband. The sensor uses the principle of the laws of reflection on interfacing surfaces between materials with differing refraction indices.

On vehicles from 2005 MY, a new second generation, combined rain and light sensor is fitted. This sensor contains four transmitter and receiver diodes for increased sensitivity and also contains a light sensor for operation of the automatic headlamp function.

Scheme 24

The rain sensor contains transmitter and receiver diodes which transmit and receive infrared light which is directed onto the windscreen via an optical unit. The light is directed at an angle so that the light is reflected 100% on the outside surface of the screen and is transmitted back into the optical unit. To receive a 100% reflection, the outer screen surface must be clean and dry.

The light is reflected four times from when it leaves the transmitter diodes to when it is picked up by the receiver diodes. If the windscreen is wet or dirty in the area of the optical unit, the clean conditions for 100% reflection means that some of the light reflected is lost. As the screen becomes dirtier or wetter, the received light is evaluated by the rain sensor and translated into a signal value. A micro-controller within the sensor monitors the change in signal and initiates the appropriate wipe cycle via K bus signals to the BCU.

The software can compensate for the long term effects of scratches and stone chips in the area of the optical unit and the short term effects of dirt or smears caused by worn wiper blades. A heater element is also contained within the rain sensor and uses ambient temperature K bus signals from the instrument pack to keep the optical unit clear of frost or condensation.

On vehicles up to 2005 MY, a light sensor is incorporated into the sensor and is used to increase the sensitivity of the sensor when light levels are low. This feature counteracts the effects of rain on the windscreen affecting the driver's vision during night time driving.

On vehicles from 2005 MY, a light sensor is used which incorporates a light guide. The light guide directs the ambient light and a proportion of the forward light (from the driving direction) to a light sensitive diode. This is used for the rain sensor sensitivity in low ambient light levels and is also used to control the automatic headlamp function fitted to vehicles from 2005 MY.

Rear Wiper

The rear wiper system comprises

1. Wiper motor and control module assembly
2. Rear washer pump
3. Wiper arm and blade.

Scheme 25

The rear wiper and washer operation is controlled by a control module which is located with the rear wiper motor. The rear wiper operation is remote from the BCU control of the front wiper systems.

The rear wiper motor and control module assembly is located in the upper tail door, behind a trim panel. The assembly is secured to a bracket on the upper tail door with three, Torx head screws. Rubber bushes isolate the motor assembly from the bracket, which help reduce the transmission of motor operating noise to the tail door.

The assembly comprises the motor, mounting bracket and control module. The motor is located on a worm drive gearbox mechanism which converts the rotary motion of the motor output spindle into the required arc for the rear wiper blade. The control module is integral with the motor and has two plug sockets which accept two multiplugs from the harness. One multiplug has 2.5 mm diameter wires. Two of the wires supply permanent battery feed and ground connections for the motor and control module. The third wire in this plug supplies a power supply to the rear washer pump. The second multiplug has 0.35 mm diameter wires and carries signal data from the wash/wipe control stalk switch and the LCM and also a power input from the passenger compartment fusebox.

The rear washer feed hose is located at the rear of the motor spindle. The hose is connected to a 90° connector allowing the washer fluid to flow through the center of the motor spindle. An NRV is located in the hose, near the motor, and prevents fluid returning to the reservoir.

The motor spindle is a conventional design with a taper spline location for the wiper arm and a threaded shank to secure the arm to the spindle.

Wiper Arm

The wiper arm is similar in design to the front wiper arms. The arm attachment hole has tapered splines which mate with the splines on the wiper spindle. The arm is secured to the wiper motor spindle with a spring washer and nut. The wiper arm has a pivot point, close to the spindle attachment. A tension spring is connected to the wiper arm on each side of the pivot point and applies pressure to maintain the wiper blade in contact with the windscreen.

The wiper blade is attached to the wiper arm with a clip that allows the blade to pivot. The blade comprises a number of levers and yokes to which the rubber wiper blade is attached. The levers and yokes ensure that the pressure applied by the arm tension spring is distributed evenly along the full length of the blade and also allow the blade to adjust to the curvature and contour of the windscreen.

A plastic cap located on the arm pivot point, covers the spindle attachment nut. The cap also contains two, adjustable ball jets, which direct washer fluid onto the tail door window. The cap, when installed, connects with the hollow motor spindle, through which the washer fluid flows to the jets.

Scheme 26

The headlamp wiper assembly is located below each headlamp. The assemblies are handed and therefore are not interchangeable. Each assembly is located on a bracket which is secured to the front panel and the headlamp. The motor is secured to the bracket with two bolts.

The headlamp wiper operation is controlled by the BCU via a headlamp wiper relay. The relay is located behind the fascia. The relay is attached to the air suspension ECU mounting bracket, above the passenger compartment fusebox and can be identified by its black color.

A 90° connector at the rear of the motor allows for the attachment of the washer fluid hose from the headlamp washer pump. The washer fluid is directed through the center of the motor drive spindle and supplies a washer jet in the spindle cover.

The motor drives a gearbox which drives the wiper blade across the headlamp in an arc. The motor spindle protrudes through a finisher below the headlamp. A tapered spline provides positive location for the wiper arm which is secured to the spindle by a nut.

The wiper arm attachment hole has tapered splines which mate with the splines on the motor spindle. The wiper arm has a pivot point, close to the spindle attachment. A tension spring is connected to the wiper arm on each side of the pivot point and applies pressure to maintain the wiper blade in contact with the headlamp lens.

A plastic cap, located on the arm pivot point, covers the spindle attachment nut. The cap also contains an adjustable ball jet, which directs washer fluid onto the headlamp lens. The cap, when installed, connects and seals onto the hollow motor spindle, through which the washer fluid flows to the jets.

The wiper blade is attached to the wiper arm with a clip that allows the blade to pivot. The blade comprises two yokes to which the rubber wiper blade is attached. The yokes ensure that the pressure applied by the arm tension spring is distributed evenly along the full length of the blade.

The front wiper system has the following functionality

1. Intermittent wipe and delay adjustment
2. Normal (slow) speed wipe
3. Fast speed wipe
4. Program wash/wipe
5. Flick wipe
6. Headlamp powerwash (if fitted)
7. 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 6.8kO resistor located in the BCU. The power supply to the voltage divider circuit is limited to 6.5V. This reduced voltage is used by the BCU to determine the position of the rotary switch as follows

ROTARY SWITCH RESISTANCE CHART

The intermittent delay is also influenced by the road speed of the vehicle using a signal value derived from the ABS ECU on the K bus. The delay periods for the vehicle stationary and when moving at different vehicle speeds are shown in the following table

ROTARY SWITCH RESISTANCE CHART

The rotary switch positions also influence the operation of the rain sensor (when fitted) by adjusting its sensitivity. Refer to Rain Sensor .

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 BCU operates the wipers in the intermittent mode, using a 3 second intermittent delay period for NAS and Australian market vehicles and a 5 second intermittent delay period for ROW vehicles.

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 optimize 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 center. The first illumination of this message is accompanied by a 'gong' sound to alert the driver to the low fluid level.

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-energizing the heater elements.

The ATC system will also prevent heated washer jet operation if the battery voltage falls to below 11 AM. 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 BCU for blocking protection of the front wiper motor. This feature protects the motor in the event of the wiper operation being obstructed.

If the BCU does not receive the wiper park signal for a period of 16 seconds, when the wiper motor is active, the BCU 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 BCU 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 is active in all wiper switch positions and can only be reset by turning the ignition off.

Rear Wipers

The rear wiper has the following functionality

1. Intermittent operation
2. Adjustable intermittent wipe period
3. 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 one 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 five complete wipe cycles. The first three wipe cycles are each accompanied by a 0.5 second operation of the rear washer pump. The final two 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 BCU to protect the rear wiper motor in the event of the wiper operation being obstructed.

Headlamp Wipers and Washers

The headlamp wipers and washers are only active when the headlamps are switched on and the ignition is on. The wipers and washers are controlled by the BCU which limits their operation to preserve washer fluid in the reservoir.

With the ignition and lights on, headlamp wash/wipe is activated on the first operation of the wiper column control switch in the wash/wipe position. The BCU then suspends headlamp wash/wipe activation for the next four operations of the wash/wipe switch, with the headlamp wipers and washers activated on the fifth operation of the switch.

The BCU monitors the operation of the wash/wipe switch and maintains a counter to restrict headlamp wiper and washer operation to every fifth operation of the wash/wipe switch. The BCU also maintains a timer which prevents a second operation of the headlamp wipers and washers within a 3 minute period. The counter and timer are reset when the ignition is switched off.

When headlamp wash/wipe is active, the BCU energizes the washer pump twice per cycle. The headlamp washer pump is powered for a 0.5 second period, 300 ms before the wiper motor starts. The BCU then initiates a 2 second delay before powering the headlamp washer 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 pack and K bus, to the BCU which suspends headlamp wash/wipe operation to preserve the remaining washer fluid.

Scheme 27

The diagnostic socket allows the transfer of information between the BCU, the rain sensor and T4. 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 sensor can store fault codes which can be used to diagnose faults or non-function of the rain 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 sensor fault prevents the sensor from operating, the BCU will control wiper operation as if a rain sensor is not installed in the system.

The BCU monitors all inputs and outputs relative to the wiper system and other BCU 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 BCU for internal and external faults. The BCU is capable of detecting open and short circuits and also incorrect K bus messages.

See also:
• Rain Sensor