ignition system LAND ROVER DISCOVERY 1995 Repair Manual

ELECTRICAL
1
DESCRIPTION AND OPERATION ELECTRICAL EQUIPMENT
DESCRIPTION
The electrical system is Negative ground, and it is
most important to ensure correct polarity of the
electrical connections at all times. Any incorrect
connections made when reconnecting cables may
cause irreparable damage to the semi-conductor
devices used in the generator and regulator. Incorrect
polarity would also seriously damage any
transistorized equipment such as radio and
tachometer etc.
WARNING: During battery removal or
before carrying out any repairs or
maintenance to electrical components
always disconnect the battery negative lead first.
If the positive lead is disconnected with the
negative lead in place, accidental contact of the
wrench to any grounded metal part could cause a
severe spark, possibly resulting in personal
injury. Upon installation of the battery the positive
lead should be connected first.
GENERATOR
The generator is a three phase, field sensed unit. The
rotor and stator windings produce three phase
alternating current, AC, which is rectified to direct
current, DC. The electronic voltage regulator unit
controls the generator output voltage by high
frequency switching of the rotor field circuit. Use only
the correct Vehicle replacement fan belt. Occasionally
check that the engine and generator pulleys are
accurately aligned.
It is essential that good electrical connections are
maintained at all times. Of particular importance are
those in the charging circuit (including those at the
battery) which should be occasionally inspected to
see that they are clean and tight. In this way any
significant increase in circuit resistance can be
prevented.Do not disconnect battery cables while the engine is
running or damage to the semi-conductor devices
may occur. It is also inadvisable to break or make any
connections in the generator charging and control
circuits while the engine is running.
The electronic voltage regulator employs micro-circuit
techniques resulting in improved performance under
difficult service conditions. The whole assembly is
encapsulated in silicone rubber and housed in an
aluminium heat sink, ensuring complete protection
against the adverse effects of temperature, dust, and
moisture etc.
The regulating voltage is set during manufacture to
give the required regulating voltage range of 14.2±
0.2 volts, and no adjustment is necessary. The only
maintenance needed is the occasional check on
terminal connections and wiping with a clean dry
cloth.
The generator system provides for direct connection
of a charge (ignition) indicator warning light, and
eliminates the need for a field switching relay or
warning light control unit. As the warning lamp is
connected in the charging circuit, lamp failure will
cause loss of charge. Lamp should be checked
regularly and spare carried.
When using rapid charge equipment to re-charge the
battery, the battery must be disconnected from the
vehicle.
NOTE: For description and operation of
electrical circuits see separate publication:
Electrical Troubleshooting Manual.

86ELECTRICAL
2
DESCRIPTION AND OPERATION ANTI-THEFT SYSTEM FUNCTION
Perimetric protection
Using the key in the correct sequence will turn on and
off perimetric protection only. When fully perimetrically
armed, all doors, and bonnet [hood] are protected
against unauthorised access. If the door key is used in
the normal manner the driver will be unaware of the
door key sequence. The time taken to lock or unlock
with the key must be less than 5 seconds. To prevent
unauthorised tampering, the alarm will sound if the
key is held in the unlocked position for longer than 5
seconds when armed. Cranking is disabled when
perimetric protection is armed.
NOTE: When key is turned left or right the
keyswitch input will be activated, in
conjunction with the sill button switch
when links are operated.
Volumetric protection
Using the handset transmitter will turn on and off
volumetric protection. In volumetric mode the vehicle
interior is protected using the ultrasonic sensor. Using
the handset also arms and disarms the vehicle
perimetrically. Cranking is disabled when volumetric
and perimetric protection is armed.
NOTE: If armed volumetrically the vehicle
CANNOT be disarmed using the key.
Alarm horn
When an intrusion is detected the alarm horn will
sound intermittently (Switzerland and Denmark
continuous horn sound) and the hazard lights flash
(where territorial regulations allow) for 30 seconds.
The alarm must be retriggered before alarm horn will
sound again.Vehicle status indication
Vehicle status is indicated by up to three devices: (a)
alarm horn, (b) hazard lights, (c) dash board LED.
When the vehicle arms in either mode the hazard
lights will flash three times and the LED will flash
rapidly for 10 seconds. LED will then flash at a slower
rate while vehicle is armed. When the vehicle disarms,
hazard lights will flash once and LED will extinguish. If
LED remains lit, it indicates that the alarm has been
triggered. Turning on ignition or arming the alarm will
extinguish LED. The LED will give a long pulse flash
to indicate the ultrasonic unit being activated.
Central locking
Central locking is controlled by the alarm ECU and
may be operated by the key, sill button(s) or handset.
The system works on both front doors on four door
vehicles or driver's door on two door vehicles.
NOTE: The central door locking system
will shut down for a short period after
more than 15 consecutive operations.
Inertia switch
An inertia switch is incorporated in the alarm system
ECU. If ignition is on and the vehicle receives an
impact sufficient to activate the inertia switch, the ECU
will signal to unlock central locking actuators and flash
hazard lights. Central locking will remain disabled for
30 seconds. To reset turn ignition off and then on after
the 30 second period has elapsed.
Ultrasonic unit
The unit operates by emitting an air pressure carrier
wave and receiving the wave back. Any disturbance
within the vehicle which disturbs the wave will be
detected, triggering the alarm.
When the volumetric sensor is activated it monitors
movement within the vehicle for 15 seconds before
detecting and responding to intrusions. If the sensor
detects movement within the vehicle it delays arming
until a 15 seconds quiet period has elapsed. If
continuous movement is detected the alarm will not
arm volumetrically.

ELECTRICAL
3
DESCRIPTION AND OPERATION Radio frequency system
The RF system uses four frequencies according to
market. If the coaxial aerial is not fitted system
performance will be impaired. Both ECU and handset
have a colour coded label.
Frequency Colour Territory
ECU/Handset
433.92 MHz Blue/black........................... UK, Ireland........................
224.5 MHz, Yellow/yellow............................ France...................
433.92 MHz Blue/Purple........................... Germany......................
433.92 MHz Blue/blue........................... Europe, not France, Switzerland, Italy, Denmark,..........................
Germany
433.92 MHz White/Blue........................... Switzerland, Denmark.......................
315.0 MHz Green/green............................. Rest of world, Italy, Australia....................
315.0 MHz Orange/Green............................. Gulf, Japan..................
Partially armed mode
If a door, tailgate or bonnet [hood] is left open when
the system is armed, the LED will not light for 10
seconds indicating a mislock condition. Hazard lights
will not flash. If an open door or tailgate is causing the
mislock, the starter motor is disabled. The alarm will
sound if ignition is turned to start position. If an open
bonnet [hood] is causing the mislock the starter motor
is disabled. The alarm will arm the volumetric part of
the system. If the door tailgate or bonnet [hood] is
subsequently closed, after a 5 second delay, the
doors will unlock and immediately lock and the system
will fully arm.
Handset transmitter
The handset LED will give one short flash when
button is pressed momentarily.
If button is held down the LED will light again after 2
seconds for 2 seconds, and extinguish until button is
released and repressed. The handset contains unique
information distinguishing it from other transmitters. It
also contains a set of 'random' rolling codes
programmed into the ECU before leaving the factory.
Each time the handset is pressed a different code is
transmitted to the ECU.
If handset is operated more than four times outside
the vehicle range (6 metres) or power supply is
removed, it will be necessary to re-sychronise handset
and the ECU by pressing the handset three times
within range and within 5 seconds.
NOTE: If both handsets are lost or
damaged when system is armed it will be
necessary to fit a new ECU with two
matching handsets.
Handset batteries
If handset LED flashes continuously when button is
pressed, the batteries need replacing. The hazard
lights will flash one 3 second pulse, instead of three
times upon arming vehicle.
Power up mode
The alarm system always remembers the state it was
left in when power was removed. If the alarm powers
up in an armed state and is subsequently triggered it
will give a warning that it will fully trigger unless
disarmed. This warning consists of short horn pulses
every two seconds for 15 seconds.
New born mode
When the ECU is first produced, it will be in its 'new
born' mode. In this mode it will respond to any remote
of the right frequency. This mode will be cancelled
when the ECU has received ten valid handset signals
without power interruption.
Engine cranking
It is only possible to crank the engine when ignition is
ON and alarm disabled.

ELECTRICAL
11
DESCRIPTION AND OPERATION ANTI-THEFT ALARM BUILT-IN TEST (96 MODELS)
NOTE: The handset should be detached
from the key to allow perimetric testing of
the alarm system. The system will
automatically switch to volumetric testing if the
handset is in close proximity to the starter switch.
The built-in test procedure can be accessed providing
the following conditions exist:
Alarm disarmed.
Ignition off.
Doors unlocked.
Bonnet[hood] closed.
The test mode can be entered by completing the
following instructions within 5 seconds:
1.Open bonnet.
2.Turn starter switch on.
3.Open driver's door (far enough to activate
switch).
4.Turn starter switch off.
5.Turn starter switch on.
If the test mode has been correctly accessed, the
sounder/horn will operate briefly and the anti-theft
alarm indicator and hazard warning lights will flash.
Perimetric tests
The anti-theft alarm indicator light and the hazard
warning lights will flash when:
1.Door switches are activated;
2.The bonnet is opened;
3.Sill switches are activated;
4.Key switches are activated.
NOTE: Operation of key switches can be
verified by turning the key in the relevent
direction so as not to simultaneously
activate the sill switch. If the key switch changes
state, the change should be detected but the sill
switch will not be activated.
Volumetric tests
Press the unlock button or move the handset close to
the starter switch to disable perimetric testing and
enable volumetric testing. If movement is detected
within the vehicle by the ultrasonic sensor it will be
indicated by flashing the anti-theft alarm indicator and
hazard warning lights.
NOTE: Exit anti-theft alarm built-in test by
turning starter switch to the off position.

ELECTRICAL
1
FAULT DIAGNOSIS GENERAL INFORMATION
The electrical fault diagnostic tool on Discovery
vehicles is Testbook. Detailed information of electrical
systems, component locations and circuit diagrams
are covered in the Discovery Electrical
Troubleshooting Manual.
See INTRODUCTION,
Information, Fault Diagnostic Equipment
This section covers checks of the charging and
ignition system.
GENERATOR TESTING
Service repair no - 86.10.01
Charging system check
1.Check battery is in good condition, with an open
circuit voltage of at least 12.6 V. Recharge or
substitute battery to carry out test.
2.Check drive belt condition.
See SECTION 10,
Maintenance, Under Bonnet [Hood]
Maintenance
3.Check battery connections are clean and tight.
4.Check generator connections are clean and
tight.
5.Ensure there is no drain on battery from, for
example, interior, under bonnet [hood] or door
edge lamps.
Generator test
Following instructions refer to use of suitable test
equipment using a carbon pile rheostat.
6.Connect test equipment referring to
manufacturer's instructions.
7.Start engine and run at 3000 rev/min without
accessory load.
8.Rotate carbon pile load control to achieve
greatest output (amps) without allowing voltage
to fall below 12.0 V. A reading in amps, of
generator output, minus 10% to allow for EFI
and Ignition loss, should be obtained.
9.Run engine at 3000 rev/min, switch selector to
regulator test, read voltmeter. A reading of 13.6
to 14.4 V should be obtained.
10.Switch selector to diode/stator test, switch on
headlamps to load generator. Raise engine
speed to 3000 rev/min, read voltmeter, needle
must be within 'OK' range.TESTING IN POSITION
Charging circuit resistance test.
1.Connect a low range voltmeter between
generator terminal marked B+ and positive
terminal of battery.2.Switch on headlamps, start engine. Run engine
at approximately 3000 rev/min. Note voltmeter
reading.
3.Transfer voltmeter connections to frame of
generator and negative terminal of battery, and
again note voltmeter reading.
4.If reading exceeds 0.5 volt on positive side or
0.25 volt on negative side, there is a high
resistance in charging circuit which must be
traced and remedied.

86ELECTRICAL
2
FAULT DIAGNOSIS LUCAS CONSTANT ENERGY IGNITION SYSTEM -
V8i
Preliminary checks
Inspect battery cables and connections to ensure they
are clean and tight. Check electrical condition of
battery.
Inspect all L.T. connections, ensure they are clean
and tight. Check H.T. leads are correctly positioned
and not shorting to ground against any engine
components. Wiring harness and individual cables
should be firmly fastened to prevent chaffing.
Pick-up air gap
Check air gap between pick-up limb and reluctor teeth
is 0.20 - 0.35 mm, using a non-ferrous gauge.
NOTE: Air gap is set initially at factory and
will only require adjusting if tampered with
or when pick-up module is replaced.
TEST 1:
H.T. Sparking
Remove coil/distributor H.T. lead from distributor
cover and hold approximately 6mm from engine block,
using suitable insulated pliers. Switch ignition 'On' and
operate starter.
Regular sparking indicates fault in H.T. distribution,
plugs, timing or fuelling, proceed to Test 6. If no spark
or weak spark occurs proceed to Test 2.TEST 2:
L.T. Voltage
Switch ignition 'On' - engine stationary.
(a) Connect voltmeter to points in circuit indicated
by V1 to V4 and make a note of voltage
readings.
(b) Compare voltages obtained with specified
values listed below:
Expected readings
V1 More than 12 volts.
V2 1 volt maximum below volts at V1.
V3 1 volt maximum below volts at V1.
V4 0 volt - 0.1 volt.
(c) If all readings are correct proceed to Test 3.
(d) Check incorrect reading(s) with chart to identify
area of possible faults, i.e. faults listed under
heading SUSPECT and rectify.
(e) If coil and amplifier is suspected, disconnect L.T.
lead at coil, repeat V3. If voltage is still incorrect,
fit new coil. If voltage is now correct, check L.T.
lead, if satisfactory fit new amplifier.
(f) If engine will not start proceed to Test 3.

ELECTRICAL
41
REPAIR COOLANT TEMPERATURE TRANSMITTER - V8i
Service repair no - 26.10.02
Remove
1.Disconnect battery negative lead.
2.Disconnect lead from transmitter.
3.Remove transmitter, discard sealing washer if
fitted.
Refit
4.Coat threads of replacement transmitter with
Loctite 572.
5.Fit a new sealing washer to transmitter.
6.Fit transmitter, connect lead.
7.Top-up cooling system.HEATED FRONT SCREEN
Heated front screen will operate when switch is
operated, with engine running. Timer unit will provide
a preset time cycle of 7« minutes±20%.
To identify timer unit.
See Electrical Trouble
Shooting Manual.Electrical Troubleshooting
Manual
Switching OFF ignition, or further operation of heated
front screen switch during cycle will switch off screen
and cancel, reset and switch off timer unit.