2002 LAND ROVER DISCOVERY battery

AIR CONDITIONING
DESCRIPTION AND OPERATION 82-27
Operation
The rear A/C only operates if the front A/C is on to pump refrigerant through the rear evaporator/blower assembly.
When the rear A/C switch is selected on, the indicator lamp in the switch illuminates and the rear blower relay is
energised. The rear blower relay switches battery power to the blower motor, which runs at the speed selected on the
blower speed switch.
The air from the blower passes through the evaporator matrix, which absorbs heat from the air. The cooled air is then
supplied to the roof vents through the distribution ducts. The heat absorbed by the refrigerant in the evaporator is
sensed by the thermostatic expansion valve. The thermostatic expansion valve then opens and regulates the flow of
refrigerant through the evaporator in proportion to the amount of heat being absorbed from the air.
When the rear A/C switch is selected off, the blower stops. The thermostatic expansion valve senses the subsequent
decrease in temperature of the refrigerant in the evaporator. The thermostatic expansion valve then closes and stops
the flow of refrigerant, except for a minimal bleed flow.

WIPERS AND WASHERS
DESCRIPTION AND OPERATION 84-9
The wiper blades are attached to the wiper arms with a clips that allow the blade to pivot. Each wiper blade comprises
a number of levers and yokes to which the rubber wiper is attached. The levers and yokes ensure that the pressure
applied by the arm spring is distributed evenly along the full length of the blade. The rubber wiper is held in the yokes
by a pair of stainless steel strips which also contribute to the even distribution of spring pressure along the blade. The
driver's side wiper blade is fitted with an aerofoil which presses the blade onto the screen at high speed. This prevents
the blade from lifting off the screen and maintains the wiping performance.
Front wash/ wipe switch
The front wash/ wipe switch is located on a stalk on the RH side of the steering column and allows the driver to control
the operation of the front wipers and the front washer pump.
Operating the washer switch provides battery voltage from fuse 19 in the passenger compartment fusebox to the
washer pump motor.
Operating the flick wipe function provides battery voltage from fuse 19 in the passenger compartment fuse box to the
high-speed brushes of the wiper motor.
Operating the intermittent function provides a battery voltage signal to the BCU. The BCU determines the wipe
interval from the variable delay switch and signals the IDM to activate the front wiper relay, which provides battery
voltage to the wiper motor.
Operating the low-speed function provides battery voltage from fuse 19 in the passenger compartment fuse box to
the low-speed brushes of the wiper motor.
Operating the high-speed function provides battery voltage from fuse 19 in the passenger compartment fuse box to
the high-speed brushes of the wiper motor

WIPERS AND WASHERS
84-10 DESCRIPTION AND OPERATION
Variable delay switch
A rotary type variable delay switch, integral with the front wash/ wipe switch, controls the interval between windscreen
wipes for intermittent wipe variable delay operation.
The variable delay switch is integral with the front wash/ wipe switch.
The input from the front variable delay switch to the BCU ranges from battery voltage to zero Volts.
The resistance values and associated time intervals of the variable delay switch are shown in the following table:
TestBook has the ability to monitor the timer function within the BCU from which it can determine the position of the
variable delay switch.
Front wiper motor assembly
The front wiper motor assembly is located on the bulkhead beneath the plenum.
Resistance, ohms Time interval, seconds
Front Rear
0 3.5 6.5
1500 5.5 10.5
3000 7.5 14.5
4500 9.5 18.5
6000 11.5 22.5

WIPERS AND WASHERS
DESCRIPTION AND OPERATION 84-11
The dc motor contains two permanent magnets, three brushes and a park switch. The smaller third brush is utilised
for high-speed operation. Attached to the brush pack are 3 capacitors, which minimise radio interference during wiper
operation. A thermal trip switch attached to the brush plate prevents thermal overload of the motor.
The motor incorporates a worm drive gear unit to transfer the rotary motion into a linear motion of the wiper linkage
assembly.
The front wiper motor receives battery voltage from fuse 19 of the passenger compartment fuse box. For low-speed
operation, including intermittent variable delay operation, the battery voltage to move the wiper motor from the park
position passes through the front wiper relay. When the park switch moves to the closed when operating position,
fuse 19 of the passenger compartment fuse box provides battery voltage directly to the wiper motor.
For high-speed operation, including flick wipe, fuse 19 in the passenger compartment fuse box provides the battery
voltage to move the wiper motor from the park position through the front wash/ wipe switch to the front wiper motor.
To achieve high-speed wiper operation, power is supplied to a third brush that provides a closer distance between the
motor poles. Because the poles of the motor are closer together, the motor operates faster.
Rear wiper
The rear wiper is driven directly from an electric motor located inside the tail door. The motor is mounted inside the
tail door with two bolts, lock washers and washers. The motor mounting brackets have rubber inserts to prevent motor
operating noise being transferred to the door structure. The motor spindle is fitted with a seal and protrudes through
a hole in the tail door outer skin panel. The motor spindle is secured to the tail door with a washer and nut.
The motor output spindle has a taper splined shaft which allows for the attachment of the wiper arm which is secured
with a nut. The wiper arm attachment to the splined shaft has a pivot to which the remainder of the arm is attached.
The two parts of the arm are connected by a spring which controls the pressure of the blade on the window to a
predetermined amount.
The wiper blade is attached to the wiper arms with a clip which allows the blade to pivot. The wiper blade comprises
of a number of levers and yokes to which the rubber wiper is attached. The levers and yokes ensure that the pressure
applied by the arm spring is evenly distributed along the full length of the blade. The rubber wiper is held in the yokes
by a pair of stainless steel strips which also contribute to the even distribution of spring pressure along the blade.
Rear wiper switch
The rear wiper switch is a latching pushbutton switch and is located on the right hand side of the instrument pack.
Activating the rear wiper switch provides an earth signal to the BCU. The BCU signals the IDM to energise the rear
wiper relay, which provides battery voltage to the rear wiper motor.

WIPERS AND WASHERS
DESCRIPTION AND OPERATION 84-13
Front screen washer jets
Two washer jets for the front windscreen are fitted to the top surface of the bonnet and held in place with plastic clips.
Each washer jet is connected via a hose to an in-line valve. The in-line valve prevents the washer fluid draining back
to the reservoir and ensures that the washers operate immediately the washer pump is operated. From each in-line
valve the washers are connected via a short hose to a 'T' connector. From the 'T' connector a single hose connects
to the outlet of the front washer pump. Each jet has two jets which can be adjusted to allow full fluid coverage of the
windscreen.
Rear screen washer jet
A single washer jet for the tail door window is fitted to the rear wiper blade. The jet has four spray orifices which direct
washer fluid to either side and along the length of the wiper blade. The jet is connected by a hose from the wiper blade,
through a sealing grommet in the tail door and connects with the rear washer hose from the rear washer pump. A non-
return valve is used to join the feed hose from the pump to the washer jet hose. The non-return valve prevents fluid
draining to the reservoir and ensures that the washer operates immediately the washer pump is operated. The hose
from the pump to the tail door is located inside the main harness.
Headlamp power washer jets
When fitted, a powerwash 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 powerwash 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.
Rear washer switch
The rear washer switch is a non-latching pushbutton switch and is located on the RH side of the instrument pack.
Activating the rear washer switch provides battery voltage from fuse 30 in the passenger compartment fusebox to the
rear washer pump.

WIPERS AND WASHERS
84-14 DESCRIPTION AND OPERATION
Front washer pump
The front washer pump consists of a DC motor with an impeller. It is located in the rear of the washer fluid reservoir
and can be identified by its black top.
Operating the front washer switch provides battery voltage to the front washer pump. This same battery voltage signal
also goes to the BCU and increments the headlamp powerwash counter providing the headlamps are switched on.
Rear washer pump
The rear washer pump consists of a DC motor with an impeller. It is located in the rear of the washer fluid reservoir
and can be identified by its red top.
Operating the rear washer switch provides battery voltage to the rear washer pump.

WIPERS AND WASHERS
DESCRIPTION AND OPERATION 84-15
Headlamp powerwash pump
The headlamp power wash pump consists of a DC motor with an impeller. It is located on the front of the washer fluid
reservoir.
The BCU controls operation of the headlamp power wash relay, which supplies battery voltage from fuse 4 located in
the engine compartment fuse box to the headlamp power wash pump. When the BCU determines headlamp power
wash is to be activated, it provides a ground path for the coil of the headlamp power wash relay. The auxiliary relay
located in the engine compartment fuse box supplies the headlamp power wash relay coil with battery voltage.

WIPERS AND WASHERS
84-18 DESCRIPTION AND OPERATION
Rear wipe
Rear wipe operation will only activate when the following conditions are met:
lIgnition switch is in position II.
lRear wipe switch is operated.
Operating the rear wiper switch provides an earth input to the BCU. The BCU tells the IDM to activate the rear wiper
relay, which provides battery voltage to the wiper motor through the normally closed contacts of the park switch.
Rear wash
Rear wash will only operate when the following conditions are met:
lIgnition switch is in position II.
lRear wash switch operated.
Operating the rear washer switch for longer than 0.4 second allows the rear washer pump motor and rear wipers to
run as long as the switch is held. The wipers run for 4 seconds after the rear washer switch is released. Flicking the
rear washer switch energises the rear washer pump motor for 0.4 second.
The rear washer operation has a higher priority than the intermittent wipe operation. If the intermittent wipe is active
when a rear washer operation is initiated, the wash cycle executes and the intermittent wipe is re-instated at the end
of the washer operation.
Wiper park switch
The park switch allows the wipers to come to rest in the park position when the wipe switch is turned off in mid-wipe.
The park switch consists of a positive and a negative contact. These two contacts are described as closed at park
and closed when operating. When the wipers first start, the park switch is in the closed at park position. A relay
controls battery voltage to the motor. Battery voltage passes through this relay contact to move the wiper motor from
the park position.
When the motor moves, the park switch moves to the closed when operating position. Battery voltage to this relay
contact is direct from fuse 19. Battery voltage passes through this contact to keep the wiper motor running. The wiper
motor operates for one complete revolution until the park switch moves to the closed at park position again.
Switching off the wipers removes battery voltage from the closed at park contact. When the wipers reach the closed
at park switch an earth is applied and the motor stops abruptly.
Headlamp power wash
Headlamp power wash activates when the following conditions are met:
lIgnition switch in position II.
lHeadlamps switched on.
lFront wash switch operated.
lBCU counter allows headlamp power wash.
Operating the front washer switch with the headlamps switched on energises the IDM, supplying a voltage to the
headlamp powerwash relay, which operates the headlamp powerwash pump and increments a counter within the
BCU. This counter prevents the headlamp powerwash pump from operating every time the front washer switch is
activated. Headlamp powerwash is only operational every third front wash cycle, providing the headlamps are on.
The counter resets when the ignition switch is turned off.
When the BCU permits headlamp power wash operation, the pump motor operates only for 0.5 second.