Land Rover Defender Electrical Library 3rd Edition Nas Rover Manual

							CIRCUIT OPERATION
DEFENDER 90 NAS15CONDENSER FAN GRANT
On receipt of the Condenser Fan Request signal, the GEMS ECM applies a ground
(C634-3) for the Condenser Fan Relay coil (C59-4). Provided that a battery feed is
available at the relay coil (C59-2) from the Main Relay within the Engine Management
Relay Module (C157-3), the Condenser Fan Relay will energize.
With the Condenser Fan Relay energized, a feed from Fuse 16 (C581-12) passes to the
relay (C59-1) on a brown and white wire, through the closed relay contacts (C59-3) to the
Condenser Fan (C48-1) on a blue and purple wire. The Condenser Fan is grounded on a
black wire.
Condenser Fan - High Engine Temperature Grant
The ECM can override the Condenser Fan Request routine and operate the fan during
high engine temperatures to assist engine cooling, regardless of whether the air-
conditioning system is operating.
When the ECM senses a high coolant temperature (above 107 
deg C - 225 deg F) via the
Engine Coolant Temperature (ECT) sensor (C636-14), the ECM will provide the grant
signal at C634-3, energizing the Condenser Fan Relay.
Condenser Fan - Hot Restart Grant
The ECM monitors engine coolant temperature when the engine is first switched off. If a
high temperature is sensed, the ECM will continue to run the fan until temperature drops,
or a pre-set time has elapsed. 
						

							CIRCUIT OPERATION
16DEFENDER 90 NASHEATER BLOWER
DESCRIPTION
The heater is operated from three sliding controls attached to the instrument binnacle.
Two of the controls regulate the temperature and air flow distribution.  The third control
operates the two speed heater blower.  The heater blower operates with the ignition
switch in position II.  
OPERATION
Feed from the positive battery terminal is connected to the engine compartment fuse box
(C632-1) by a brown wire.  Current passes through fusible link 1 and fusible link 5 of the
engine compartment fuse box which are connected in series. Fusible link 5 (C570-2) is
connected to  the ignition switch  (C28-1) by the brown wire.  
With the ignition switch in position I, power flows through the ignition switch (C99-1) to
fuse 4 (C580-7) of the passenger compartment fuse box on the white/orange wire.  Fuse 4
(C580-8) of the passenger compartment fuse box is connected to the blower fan motor
(C56-3) by the purple/green wire. When the blower control is in the off position, the
blower motor  has no route to ground and does not run.   
Moving the blower control to position 1 connects the blower motor (C56-2) to the blower
switch (C58-2) on the green/slate wire.  Power flows through the blower motor and
resistor to the blower switch (C58-2) on the green/slate wire and to ground on the black
wire.  The blower fan operates at low speed.  
Moving the blower control to position 2 connects the blower motor (C65-1) directly to
the blower switch (C58-1) on the green/slate wire and to ground on the black wire.  The
blower fan operates at high speed.  
						

							CIRCUIT OPERATION
DEFENDER 90 NAS17HEATED REAR WINDOW  
DESCRIPTION  
The heated rear window (HRW) draws a high current from the electrical system and to
prevent battery discharge, the HRW will only operate when the engine is running. The
functionality of the HRW is controlled by the multi-function ECU.  The HRW is operated
by depressing the non latching heated rear window switch, mounted on the dash panel.
The instrument panel warning light will illuminate to indicate that the HRW is operating.
The ECU will power the HRW for approximately 15 minutes from the first press of the
HRW switch or until the ignition is switched off or the HRW switch is pressed for a
second time. If the engine stops running while the HRW is powered, the ECU will switch
off power to the HRW.  The switch is illuminated when the sidelights are switched on.  
OPERATION  
Feed from the positive battery terminal is connected to the engine compartment fuse box
(C632-1) by the brown wire.  Current passes through fusible link 1 and fusible link 5 of
the engine compartment fuse box which are connected in series. Fusible link 5 (C570-2)
is connected to  the ignition switch  (C28-1) by the brown wire.  
With the ignition switch in position II, power flows across the ignition switch (C94-1)
and supplies fuse 1 of the passenger compartment fuse box (C580-1) on the white wire.
Fuse 1 is connected to the ECU (C16-5), via a header joint (C287), by the white/green
wire.  The ECU (C16-4) is connected to the oil pressure switch (C187-1), via a header
joint (C228), by the white/brown wire and receives a ground signal if the engine is not
running.  The ECU (C16-2) is connected to the HRW switch (C947-5) by the white/red
wire.  The ECU (C16-6) is grounded by the black wire.  
With the engine running, depressing the HRW switch momentarily provides an route to
ground for the ECU on the white/red wire, via the HRW switch (C947-2) and to ground
on the black wire.  On sensing the ground signal, the ECU switches a feed from fuse 1 of
the engine compartment fuse box to the HRW relay winding.  Fuse 2 of the engine
compartment fuse box (C574-3) is connected to the ECU (C16-1) by the purple wire.
The ECU (C62-2) is connected to the HRW relay winding (C44-87) by the white/pink
wire.  The HRW relay winding (C44-86) is grounded by the black wire.  When the HRW
relay is energized, the HRW relay switches power supply from fusible link 6 of the engine
compartment fuse box to the HRW element and instrument pack warning light.  Fusible
link 6 (C573-3) of the engine compartment fuse box is connected to the HRW relay (C44-
8) by the brown/slate wire.  The HRW relay (C44-30) is connected to the HRW element
(C702-2) and instrument pack warning light (C929-1) by the white/black wires.  The
HRW element is grounded to the rear door frame.  The instrument pack warning light is
grounded by the black wire.   
						

							CIRCUIT OPERATION
18DEFENDER 90 NASIllumination  
The HRW switch has illumination which operates with the sidelights.  Power from fusible
link 1 of the engine compartment fuse box passes through fusible link 4 of the engine
compartment fuse box (C573-2) and feeds the lighting switch (C41-1) on a brown wire.
The lighting switch (C41-2) is connected to fuse 11 of the passenger compartment fuse
box (C581-1) by a red wire.  When the lighting switch is turned on, power is supplied
through fuse 11 (C581-2) to the dimmer circuit header joint (C285-7) on the red/black
wire - (See interior illumination).  Power flows through the switch (C201-2) to the HRW
switch illumination (C947-7) on the red/white wire. The HRW switch illumination is
grounded on a black wire.  
						

							CIRCUIT OPERATION
DEFENDER 90 NAS19WIPERS AND WASHERS  
DESCRIPTION  
The front windscreen wipers are controlled from the column switch and operate when the
ignition switch is in position II.  The wipers have 2 speed settings, along with 2 flick
wipe speeds and a single wipe facility.  An intermittent wipe function and programmed
wash wipe facility is controlled by the multi-function ECU.  
Moving the wiper switch down from the off position initiates the intermittent wipe
function.  Moving the wiper switch  up one position from the off position, operates the
wipers at slow speed.  Moving the wiper switch up 2 positions from the off position,
operates the wipers at fast speed.  Pushing the wiper switch up from the off position,
against spring pressure, and releasing the switch causes the wipers to perform a single
wipe cycle at slow speed. Pressing the end of the wiper switch initiates the programmed
wash wipe sequence, windscreen washers operate while the switch is pressed and the
wipers continue to operate for a number of cycles after the switch is released.  
The rear windscreen wiper and rear wash facilities are controlled from two switches
mounted to the dash panel.  
Pressing the wiper switch causes the rear wiper to operate until the switch is turned off.
Pressing the washer switch causes the rear washer to operate until the switch is released,
the rear wiper also performs a number of cycles.  
OPERATION  
Feed from the positive battery terminal is connected to the engine compartment fuse box
(C632-1) by the brown wire.  Current passes through fusible link 1 and fusible link 5 of
the engine compartment fuse box which are connected in series. Fusible link 5 (C570-2)
is connected to the ignition switch  (C28-1) by the brown wire. With the ignition switch in
position II power flows across the switch (C94-1) to fuse 1 (C580-1), fuse 17 and fuse
18 (C581-13) of the passenger compartment fuse box on white wires. Fuse 17 supplies
the rear wash/wiper circuit, fuse 1 and fuse 18 supply the front wash/wiper circuit.  
Front wipers and washers  
Fuse 2 of the engine compartment fuse box (C574-3) provides a permanent 12 volt feed
to the ECU (C16-1) on the purple wire.  Fuse 1 of the passenger compartment fuse box
(C580-2) supplies the ECU (C16-2) with a 12 volt feed on the white/green wire when the
ignition switch is in position II.   
						

							CIRCUIT OPERATION
20DEFENDER 90 NASSlow and fast speeds  
Fuse 18 of the passenger compartment fuse box (C581-16) is connected to the wash/wipe
switch (C278-6) via a header joint (C289) by the green wire. Moving the switch to the
slow speed position allows power to flow across the switch (C278-1) to the wiper motor
(C30-3) on the blue/light green wire.  The wiper motor is grounded (C30-1) on the black
wire and the wipers operate at slow speed. Moving the wiper switch to the fast position
allows power to flow through the switch (C278-5) to the wiper motor (C30-5) on the
red/light green wire. The wiper motor is grounded (C30-1) on the black wire and the
wipers operate at fast speed.
Park circuit  
Positioning the wiper switch to the off position cuts power to the wiper motor on the
blue/light green or red/light green wire. The park circuit operates to return the wipers to
their park position. The park switch (C30-4), integral to the wiper motor unit, receives a
12 volt supply from fuse 18 of the passenger compartment fuse box (C581-16) via a
header joint (C289) on the green wire.  The park switch is closed with the wipers in any
position other than their park position.  With the park switch closed, power flows through
the switch (C30-2) to the front wiper relay (C39-5) on the brown/light green wire. The
front wiper relay (C39-2) is connected to the wiper switch (C278-4) by the yellow/light
green wire. Power flows through the wiper switch (C278-1) to the wiper motor (C30-3)
on the blue/light green wire.  The wiper motor is grounded on the black wire. The wipers
operate until their park position is reached and the park switch opens, cutting power
supply to the wiper motor.  
Intermittent wiper function  
Moving the wiper switch to the intermittent wipe position allows power to flow across the
switch (C278-3) to the ECU (C62-9) on the light green/green wire. With a 12 volt signal
applied to the ECU from the wiper switch, the ECU switches the route to ground (C62-
22) for the front wiper relay winding (C39-4) on and off approximately every 6 seconds,
on the brown/slate wire. The front wiper relay (C39-8) and winding (C39-6) are powered
from fuse 18 of the passenger compartment fuse box (C581-16) via a header joint (C289)
on green wires.  
With the front wiper relay energized, power flows across the relay (C39-2) to the wiper
switch (C278-4) on the yellow/light green wire.  Power flows through the wiper switch
(C278-1) to the wiper motor (C30-3) on the blue/light green wire.  The wiper motor is
grounded (C30-1) on the black wire and operates at slow speed. After approximately 1
second, the ECU de-energizes the front wiper relay and the wipers continue operating 
						

							CIRCUIT OPERATION
DEFENDER 90 NAS21through the park circuit until their park position is reached.  Approximately 5 seconds
later, the ECU energizes the front wiper relay for 1 second. The process repeats until
power to the ECU from the wiper switch is broken by positioning the wiper switch to the
off position or slow speed wipe position.  
Programmed wash/wipe function  
Depressing the end of the wiper switch operates the programmed wash/wipe function.
The washer switch (C278-6) is supplied from fuse 18 of the passenger compartment fuse
box (C581-16), via a header joint (C289), on the green wire. When the switch is closed,
power flows through the switch (C278-2) to the windscreen washer pump (C8-2) and
ECU (C62-13), via a header joint (C288), on light green/black wires.  The washer pump
(C8-1) is grounded on the black wire and operates until the washer switch is released.
With a 12 volt supply applied to the ECU from the washer switch, the ECU energizes the
front wiper relay by grounding the relay winding (C39-4) on the brown/slate wire. With
the front wiper relay energized, power flows across the relay (C39-2) to the wiper switch
(C278-4) on the yellow/light green wire.  Power flows through the wiper switch (C278-1)
to the wiper motor (C30-3) on the blue/light green wire.  The wiper motor is grounded
(C30-1) on the black wire and operates at slow speed.  When power to the ECU (C62-13)
is cut, by releasing the washer switch, the ECU continues to energize the front wiper
relay for a time to allow approximately 2 further cycles of the front wipers.  After the
front wiper relay has been de-energized, the park circuit returns the wipers to their park
position.   
Rear wiper  
Fuse 17 of the passenger compartment fuse box (C581-14) feeds the rear wiper switch
(C79-5) on the green wire. Closing the rear wiper switch allows power to flow through
the switch (C79-2) to the ECU (C62-15) on the red/light green wire.  With a 12 volt feed
from the switch to the ECU, the ECU (C62-23) switches the route to ground from the rear
wiper relay winding (C124-86) on the brown/purple wire.  The rear wiper relay (C124-
87) and winding  (C124-85) are supplied from fuse 17 of the passenger  compartment
fuse box (C581-14) on  green wires.  With the rear wiper relay energized, power flows
through the relay (C124-30) to the rear wiper motor (C835-1) on the brown/light green
wire.  The rear wiper motor is grounded (C388-1) on the black wire.  When power from
the rear wiper switch to the ECU is cut, the rear wipe park circuit operates to return the
wiper to the park position. When the rear wiper is in any position other than the park
position, the park switch (C835-2), integral to the motor, receives a 12 volt supply from
fuse 17 of the passenger compartment fuse box on the green wire.  Power flows through
the park switch and wiper motor to ground on the black wire. When the wiper reaches its
park position, the park switch opens and power to the wiper motor is cut.   
						

							CIRCUIT OPERATION
22DEFENDER 90 NASRear wash  
The rear wash switch (C73-5) is supplied from fuse 17 of the passenger compartment fuse
box (C581-14) on the green wire.  Depressing the wash switch allows power to flow
through the switch (C73-2) to the rear washer pump (C21-2) and ECU (C62-16) on
black/light green wires. The washer pump (C21-1) is grounded on the black wire and
operates until the switch is released. When the ECU receives a 12 volt signal from the
washer switch, the ECU energizes the rear wiper relay by grounding the relay winding
(C124-86) on the brown/purple wire. The rear wiper relay (C124-87) and winding
(C124-85) are supplied from fuse 17 of the passenger  compartment fuse box (C581-14)
on  green wires.  With the rear wiper relay energized, power flows through the relay
(C124-30) to the rear wiper motor (C835-1) on the brown/light green wire.  The rear
wiper motor is grounded (C388-1) on the black wire.  Releasing the rear washer switch
cuts the power supply to the ECU, however the ECU continues to provide a route to
ground for the rear wiper relay  for a time to allow the rear wiper to complete
approximately 3 further wipe cycles.  When the ECU de-energizes the rear wiper relay,
the rear wiper park circuit operates to return the rear wiper to the park position.   
						

							CIRCUIT OPERATION
DEFENDER 90 NASREV: 9/9723EXTERIOR LAMPS - Brake and Reverse Lamps  
DESCRIPTION  
The brake lights on the rear of the vehicle illuminate with the ignition switched on and the
brake pedal depressed.  
The reverse lights on the rear of the vehicle illuminate with the ignition switched on and
the gear selector lever in reverse position.  
OPERATION  
Feed from the positive battery terminal is connected to the engine compartment fuse box
(C632-1) by the brown wire.  Current passes through fusible link 1 and fusible link 5 of
the engine compartment fuse box which are connected in series. Fusible link 5 of the
engine compartment fuse box (C570-2) is connected to the ignition switch (C028-1) by
the brown wire.  
When the ignition switch is in position II, power flows across the ignition switch (C94-1)
to fuses 17 and 18 of the passenger compartment fuse box (C581-13) on the white wire.
Fuse 17 of the passenger compartment fuse box feeds the brake light circuit.  Fuse 18 of
the passenger compartment fuse box feeds the reverse light circuit.  
Brake lights  
Fuse 17 (C581-14) of the passenger compartment fuse box is connected to the brake
pedal switch (C75-1) by the green wire.  When the brake pedal is depressed, the brake
pedal switch closes and power flows through the switch.  The brake pedal switch (C029-
1) is connected to the LH tail light (C404-2), RH tail light (C401-2), trailer connector
(C029-1) and high mounted brake light harness (C406-1) by green/purple wires.  The high
mounted brake light (C972-1) is supplied a feed via a separate harness on a red wire. All
brake lights are grounded on black wires.  
Reverse light  
Fuse 18 (C581-16) is connected to starter inhibitor/reverse light switch (C69-2) by the
green wire.  When the gear selector is in the reverse position, the reverse light switch is
closed. Current from fuse 18 flows across the reverse light switch (C69-3) to the reverse
light (C167-1) and trailer connector (C699-1) by green/brown wires.  Both reverse light
and trailer connector are grounded by black wires.  
						

							CIRCUIT OPERATION
24DEFENDER 90 NASEXTERIOR LAMPS - Head, Side and Number Plate Lamps 
DESCRIPTION  
The lights are operated from the lighting switch located on the steering column. The
lighting switch has 2 positions. Position 1 switches on the tail lights and front sidelights,
position 2 additionally switches on the front headlights.  When the headlights are on, the
column switch can be used to switch between main beam and dipped beam.  
The headlights can be flashed with the lights on or off, by pulling the column switch
towards the driver.  
OPERATION  
Side lights  
Feed from the positive battery terminal is connected to the engine compartment fuse box
(C632-1) by the brown wire.  Current passes through fusible link 1 and fusible link 4 of
the engine compartment fuse box which are connected in series. Power from fusible link 4
of the engine compartment fuse box (C573-2) feeds the lighting switch (C41-1) on a
brown wire. With the lighting switch in the side lights position, power flows through the
light switch (C41-2) to passenger compartment fuse box (C581-1) fuses 11 and 12 on a
red wire. Fuse 11 feeds the trailer connector (C499-7), number plate illumination light
(C139-1), LH tail light (C404-3), LH rear side marker light (C405-1), LH front side
marker light (C13-1) and LH front side light (C538-1).  All lights are grounded on black
wires. Fuse 12 feeds the trailer connector (C499-1), RH tail light (C401-3), RH rear side
marker light (C400-1), RH front side marker light (C12-1) and RH front side light (C537-
1).  All lights are grounded on black wires.   
Headlights  
Fusible link 5 of the engine compartment fuse box (C570-2) is connected to the ignition
switch  (C28-1) by the brown wire. With the ignition switch in position II, power flows
across the ignition switch (C94-1) to fuse 1 of the passenger compartment fuse box
(C580-1) on the white wire.  Fuse 1 is connected to the headlight solenoid winding
(C282-85) by the white/green wire.  The headlight solenoid winding is grounded (C282-
86) on a black wire.  With the headlight solenoid energized, the relay switches to allows
power to flow across the relay.  
When the lighting switch is in the headlight position, power from fusible link 4 of the
engine compartment fuse box flows through the lighting switch (C41-4) to the headlight
relay (C282-87) on a blue/yellow wire.  Provided the solenoid is energized, by the
ignition being switched on, power flows through the headlight relay (C282-30) to the
column switch (C36-1) on a blue wire.