relay LAND ROVER DISCOVERY 1995 Service 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.

ELECTRICAL
5
DESCRIPTION AND OPERATION ANTI THEFT ALARM SYSTEM
The main function of the system is to offer easy to use
remote locking and unlocking of the vehicle without
having to actively select the alarm function.
ALARM COMPONENTS
COMPONENT LOCATION
1. Electronic control unit (ECU) and relays Passenger footwell.................
2. Bonnet switch RH engine bay..........................................................
3. Door switches
4. Alarm sounder RH engine bay.........................................................
5. Light emitting diode (LED) Dash panel.......................................
6. Ultrasonic unit Roof map pocket.........................................................
7. Lock barrel, sill buttons
8. Handset transmitter
9. Aerial 'A' post, passenger side........................................................................

86ELECTRICAL
6
DESCRIPTION AND OPERATION ALARM COMPONENT LOCATIONS (96 MODELS)
COMPONENT LOCATION
1. Electronic control unit (ECU) and relays Under dash (passenger side).................
2. Anti-theft alarm indicator light Instrument panel..................................
3. Engine immobilisation warning light (EIWL) * Instrument panel..........
4. Passive coil Over starter switch barrel.............................................................
5. Bonnet switch RH engine compartment..........................................................
6. Door switches
7. Ultrasonic sensor Interior light switch panel....................................................
8. Lock barrel, sill buttons
9. Handset and key
10. Battery backed-up sounder or horn * RH engine compartment......................
11. Immobilisation unit (spider) * Above heater...................................
12. Aerial Part of fascia harness.......................................................................
* where applicable

ELECTRICAL
7
DESCRIPTION AND OPERATION ANTI-THEFT ALARM DESCRIPTION (96 MODELS)
NOTE: The alarm system provides security
protection under wide ranging
circumstances and is fully programmable
to meet market requirements; consequently some
of the features listed will vary dependent on
vehicle model or territory.
The handset is intended to be the primary source of
control for the alarm system. The key should only be
used in the event of handset failure or if perimetric
arming only is required.
Immobilisation
After a time period the vehicle is automatically
immobilised regardless of whether or not the alarm is
armed.
Mobilisation
The handset provides the normal means of
mobilisation. In the event of handset failure, the key
may be used to enter the emergency key access
code.
Perimetric arming
Provides protection whilst the vehicle is still occupied.
Volumetric arming
If movement within the vehicle is detected the alarm
will be triggered.
NOTE: Perimetric arming always
accompanies volumetric arming.
Built-in test
The alarm system has a built-in test procedure, but if
possible any fault finding should normally be
undertaken using TestBook.
Emergency key access (EKA)
In the event of handset failure the alarm can be
disarmed by entry of the EKA code which is unique to
each vehicle.CONTROL SYSTEM
Electronic control unit (ECU) and relays
The ECU is the alarm system 'brain' and controls all
alarm functions. It responds to inputs received, by
supplying suitable outputs to indicate the status of the
alarm system or activating the relevant warning
devices.
Handset
The handset is the primary source of control for the
alarm system i.e. it locks and unlocks the vehicle,
arms and disarms the alarm.
Door key
The vehicle may be locked using the key (perimetric
arming only).
NOTE: The vehicle MUST be unlocked
using the handset. The key may be used to
unlock the vehicle if the handset fails to
operate, see operation, Emergency key access.
Passive coil
The passive coil is located around the starter switch
and triggers the handset (usually located on the
keyring) if it is within close proximity.
Aerial
The aerial is a floating connection which supplies the
alarm ECU with the signal received from the handset.
Immobilisation unit (spider)
Dependent on model or territory, the system may be
fitted with an immobilisation unit which is discreetly
located and provides an interface between the ECU
and immobilised areas of the vehicle.

ELECTRICAL
43
REPAIR ANTI-THEFT ALARM ECU (96 MODELS)
Service repair no - 86.55.85
Remove
1.Remove 4 studs securing fascia left hand
closing panel.
2.Remove closing panel.
3.Disconnect 2 multiplugs from ECU.
4.Remove nut securing ECU/relay bracket.
5.Lower bracket.
6.Remove 2 nuts securing ECU to bracket.
7.Remove ECU.
NOTE: A new ECU must be initialised
using TestBook.
Refit
8.Reverse removal procedure.HANDSET (96 MODELS)
If vehicle does not respond to handset immediately, it
may have lost synchronisation. To re-synchronise,
press either button, 4 times in quick succession. If
handset still fails to respond, check batteries, refer to
Owner's handbook. If batteries are okay, it may be
necessary to use emergency key access, refer to
Owner's handbook.
NOTE: New handsets must be initialised
using TestBook.
PASSIVE COIL (96 MODELS)
Service repair no - 86.77.35
Remove
1.Remove steering column shroud.
See
STEERING, Repair, Steering column shroud
2.Release multiplug from harness clip and
disconnect.
3.Release passive coil from starter switch.
4.Remove bulb holder/starter switch shroud.
5.Remove coil.
Refit
6.Fit coil, ensuring switch illumination bulb harness
passes through large cut-out.
7.Secure coil with cable tie.
8.Position bulb holder/starter switch shroud and
locate bulb.
9.Locate bulb holder/starter switch shroud,
ensuring cut-out in shroud aligns with lug on
starter switch.
10.Connect multiplug and secure to clip.
11.Fit column shroud.