si board BMW 3 SERIES 1989 E30 User Guide

SI board is a self-contained computer which
includes a chip and batteries.
The rechargeable SI board nickel cadmium
(nicad) batteries maintain power to the
computer memory in the event of a power
drop (such as during starting) or complete
power loss (such as a dead or disconnected
battery) (see illustration). This assures power
so the computer can continue to keep track of
mileage and turn the lights on at the proper
interval.
The batteries have a life of approximately
six years, at which time they must be replaced
with new ones. Also, since they are recharged
by the engine charging system, they can run
down prematurely if power is cut off for some
reason (such as a blown fuse, a fault in the
wiring, or extended storage of the vehicle).
Excessive heat or cold can also shorten
battery life, with heat the greatest enemy.
Extreme heat can cause the batteries to
actually split open, allowing acid to drip into
the instrument cluster.
Several instruments controlled by the SI
board can be affected by low or discharged
batteries. Symptoms of low or dead SI board
batteries can include inconsistent tachometer
and temperature gauge readings, background
radio noise, and the inability to turn the
service lights off with the special tool.
Although only complete SI boards are
available from the manufacturer, batteries are
available separately from aftermarket sources.
While it is possible for the home mechanic to
renew the batteries, they are soldered to the
board, so unless you are skilled at this and
have the proper tools, this job should be left
to an experienced electronics technician.
Considerable savings can be realised by
removing the instrument cluster (see
Section 10) and taking it to an electronics
specialist.
Caution: the instrument cluster
and components are very
susceptible to damage from
static electricity. Make sure you
are earthed and have discharged any
static electricity (by touching an object
such as a metal water pipe) before
touching the cluster components.12 Headlights- bulb renewal
1
Caution: If the radio in your
vehicle is equipped with an anti-
theft system, make sure you have
the correct activation code
before disconnecting the battery, Refer to
the information on page 0-7 at the front of
this manual before detaching the cable.
Note: If, after connecting the battery, the
wrong language appears on the instrument
panel display, refer to page 0-7 for the
language resetting procedure.
1Disconnect the battery negative cable.
Sealed-beam type
2Remove the grille (see Chapter 11).
3Remove the headlight retainer screws,
taking care not to disturb the adjustment
screws.
4Remove the retainer and pull the headlight
out enough to allow the connector to be
unplugged.
5Remove the headlight.
6To refit the headlight, plug the connector in,
place the headlight in position, and refit the
retainer and screws. Tighten the screws
securely.7Refit the grille. Connect the battery negative
cable.
Halogen bulb type
Warning: Halogen gas-filled bulbs
are under pressure, and may
shatter if the surface is scratched
or the bulb is dropped. Wear eye
protection, and handle the bulbs carefully,
grasping only the base whenever possible.
Do not touch the surface of the bulb with
your fingers, because the oil from your
skin could cause it to overheat and fail
prematurely.
8From behind the headlight assembly,
remove the outer cover (see illustration).
9Twist and release the inner cover from the
rear of the headlight (see illustration).
10Disconnect the wire from the rear of the
headlight bulb (see illustration).
11Release the clips, and withdraw the bulb
from the headlight unit (see illustration).
12Fit the new bulb using a reversal of the
removal procedure. Make sure that the clips
engage the bulb correctly.
13Connect the battery negative cable.
Body electrical systems 12•5
12.9 Twist and release the headlight inner
cover12.8 Removing the headlight rear outer
cover (3-Series shown)11.2 These batteries (arrowed) power the
Service Indicator (SI) board
12.11 Removing the headlight bulb (do not
touch the surface of the bulb with your
fingers)12.10 Disconnecting the wire from the rear
of the headlight bulb
12
If you do touch the headlamp
bulb surface, clean it with
methylated spirit.

12•18 Wiring diagrams
Typical wiring diagram for the central locking, burglar alarm, on-board computer, additional heater and digital clock (1 of 2)

Wiring diagrams 12•19
12
Typical wiring diagram for the central locking, burglar alarm, on-board computer, additional heater and digital clock (2 of 2)

12•20 Wiring diagrams
Key to wiring diagram for the central locking, burglar alarm, on-board computer, additional heater and digital clock

REF•22Glossary of Technical Terms
EEGR valveA valve used to introduce exhaust
gases into the intake air stream.
Electronic control unit (ECU)A computer
which controls (for instance) ignition and fuel
injection systems, or an anti-lock braking
system. For more information refer to the
Haynes Automotive Electrical and Electronic
Systems Manual.
Electronic Fuel Injection (EFI)A computer
controlled fuel system that distributes fuel
through an injector located in each intake port
of the engine.
Emergency brakeA braking system,
independent of the main hydraulic system,
that can be used to slow or stop the vehicle if
the primary brakes fail, or to hold the vehicle
stationary even though the brake pedal isn’t
depressed. It usually consists of a hand lever
that actuates either front or rear brakes
mechanically through a series of cables and
linkages. Also known as a handbrake or
parking brake.
EndfloatThe amount of lengthwise
movement between two parts. As applied to a
crankshaft, the distance that the crankshaft
can move forward and back in the cylinder
block.
Engine management system (EMS)A
computer controlled system which manages
the fuel injection and the ignition systems in
an integrated fashion.
Exhaust manifoldA part with several
passages through which exhaust gases leave
the engine combustion chambers and enter
the exhaust pipe.
FFan clutchA viscous (fluid) drive coupling
device which permits variable engine fan
speeds in relation to engine speeds.Feeler bladeA thin strip or blade of hardened
steel, ground to an exact thickness, used to
check or measure clearances between parts.
Firing orderThe order in which the engine
cylinders fire, or deliver their power strokes,
beginning with the number one cylinder.
Flywheel A heavy spinning wheel in which
energy is absorbed and stored by means of
momentum. On cars, the flywheel is attached
to the crankshaft to smooth out firing
impulses.
Free playThe amount of travel before any
action takes place. The “looseness” in a
linkage, or an assembly of parts, between the
initial application of force and actual
movement. For example, the distance the
brake pedal moves before the pistons in the
master cylinder are actuated.
FuseAn electrical device which protects a
circuit against accidental overload. The typical
fuse contains a soft piece of metal which is
calibrated to melt at a predetermined current
flow (expressed as amps) and break the
circuit.
Fusible linkA circuit protection device
consisting of a conductor surrounded by
heat-resistant insulation. The conductor is
smaller than the wire it protects, so it acts as
the weakest link in the circuit. Unlike a blown
fuse, a failed fusible link must frequently be
cut from the wire for replacement.
GGapThe distance the spark must travel in
jumping from the centre electrode to the sideelectrode in a spark plug. Also refers to the
spacing between the points in a contact
breaker assembly in a conventional points-
type ignition, or to the distance between the
reluctor or rotor and the pickup coil in an
electronic ignition.
GasketAny thin, soft material - usually cork,
cardboard, asbestos or soft metal - installed
between two metal surfaces to ensure a good
seal. For instance, the cylinder head gasket
seals the joint between the block and the
cylinder head.
GaugeAn instrument panel display used to
monitor engine conditions. A gauge with a
movable pointer on a dial or a fixed scale is an
analogue gauge. A gauge with a numerical
readout is called a digital gauge.
HHalfshaftA rotating shaft that transmits
power from the final drive unit to a drive
wheel, usually when referring to a live rear
axle.
Harmonic balancerA device designed to
reduce torsion or twisting vibration in the
crankshaft. May be incorporated in the
crankshaft pulley. Also known as a vibration
damper.
HoneAn abrasive tool for correcting small
irregularities or differences in diameter in an
engine cylinder, brake cylinder, etc.
Hydraulic tappetA tappet that utilises
hydraulic pressure from the engine’s
lubrication system to maintain zero clearance
(constant contact with both camshaft and
valve stem). Automatically adjusts to variation
in valve stem length. Hydraulic tappets also
reduce valve noise.
IIgnition timingThe moment at which the
spark plug fires, usually expressed in the
number of crankshaft degrees before the
piston reaches the top of its stroke.
Inlet manifoldA tube or housing with
passages through which flows the air-fuel
mixture (carburettor vehicles and vehicles with
throttle body injection) or air only (port fuel-
injected vehicles) to the port openings in the
cylinder head.
Exhaust manifold
Feeler blade
Adjusting spark plug gap
Gasket
EGR valve

REF•27
REF
Index
R
Radiator - 3•3, 11•4
Radio - 12•4
Receiver-drier - 3•9
Regulator (voltage) - 5•10
Regulator (window) - 11•8
Relays - 12•2
Repair procedures - REF•8
Respraying - 11•3
Reversing light switch - 7B•4
Rocker arms - 2B•11
Rotor - 1•18
Routine maintenance and servicing- 1•1
et seq
Routine maintenance - air conditioning
system - 3•8
Routine maintenance - bodywork and
underframe - 11•1
Routine maintenance - hinges and locks -
11•4
Routine maintenance - interior trim - 11•2
Routine maintenance - upholstery and
carpets - 11•2
Rust holes in bodywork - 11•2
S
Safety first! - 0•5
Scalding - 0•5
Scratches in bodywork - 11•2
Screw threads and fastenings - REF•8
Seat belt - 11•9, REF•2
Seats - 11•9, REF•2
Selector lever - 7B•3, 7B•5
Selector shaft - 7A•2
Service Indicator (SI) board - 12•4
Service indicator light - 1•26
Servo - 9•2, 9•10, 9•11
Shock absorber - 1•21, 10•7, 10•8, 10•9,
REF•2, REF•3
Shoes - 9•7
Short-circuit - 12•2Silencer - 4•20
Slave cylinder - 8•3
Spares - REF•19
Spark plug - 1•17, 1•18
Speed sensors - 5•8
Springs - 10•7, 10•9, REF•3
Starter inhibitor - 7B•4
Starter motor - 5•12
Starter motor fault - REF•10
Starting system - 5•11
Steering box - 10•15
Steering column - 11•9, 12•3, REF•1
Steering gear - 10•12, 10•13, REF•3
Steering linkage - 10•14
Steering wheel - 10•16, REF•1
Stop-light switch - 9•13
Struts - 1•21, 10•6, 10•7
Sump - 2A•15
Supplemental Restraint System (SRS) -
12•8
Suspension and steering systems- 1•21,
1•22, 10•1et seq, REF•2, REF•3
Suspension and steering fault finding -
REF•15
Switches - 7B•4, 9•13, 12•3
T
Tailgate - 11•6
Tappets - 2B•11
Thermostat - 3•2
Thermotime switch - 4•17, 4•18
Throttle body - 4•16
Throttle linkage - 1•20
Throttle Position Sensor (TPS) - 6•3
Throttle positioner - 4•13, 4•14
Thrust arm - 10•5
Timing - 5•4
Timing belt - 1•26, 2A•8, 2A•9
Timing chain - 2A•6, 2A•8
Timing sensors - 6•4
Tools - REF•5, REF•7, REF•8
Top Dead Centre (TDC) for No 1 piston -
2A•3Torque converter - 7B•5
Towing - 0•8
Track rod ends - 10•13
Trailing arms - 10•10
Transmission - SeeManual transmission or
Automatic transmission
Trim - 11•2, 11•6
Tyres - 1•9, 1•14, 10•16, REF•4, REF•15
U
Underframe - 11•1
Universal joints - 8•8
Upholstery - 11•2
V
Vacuum hoses - 1•14
Vacuum servo - 9•10
Valve clearances - 1•19
Valve cover - 2A•4
Valves - 2B•10, 2B•11
Vehicle identification - REF•2, REF•19
Voltage checks - 12•1
Voltage regulator - 5•10
W
Washer fluid - 1•9
Water pump - 3•5
Weekly checks- 1•7et seq
Wheel alignment - 10•17
Wheel bearings - 10•8, 10•11, REF•3
Wheel changing - 0•8
Wheels - 10•16, REF•4
Windows - 11•8, 12•9
Windscreen - REF•1
Wiper blades - 1•23
Wiper motor - 12•7
Wiring diagrams- 12•9et seq
Working faclities - REF•7