1989 BMW 3 SERIES ECU

it to the approximate size and shape required,
then pull off the backing paper (if used) and
stick the tape over the hole; it can be
overlapped if the thickness of one piece is
insufficient. Burnish down the edges of the
tape with the handle of a screwdriver or
similar, to ensure that the tape is securely
attached to the metal underneath.
Bodywork repairs - filling and
respraying
Before using this Section, see the Sections
on dent, deep scratch, rust holes and gash
repairs.
Many types of bodyfiller are available, but
generally speaking, those proprietary kits
which contain a tin of filler paste and a tube of
resin hardener are best for this type of repair. A
wide, flexible plastic or nylon applicator will be
found invaluable for imparting a smooth and
well-contoured finish to the surface of the filler.
Mix up a little filler on a clean piece of card
or board - measure the hardener carefully
(follow the maker’s instructions on the pack),
otherwise the filler will set too rapidly or too
slowly. Using the applicator, apply the filler
paste to the prepared area; draw the
applicator across the surface of the filler to
achieve the correct contour and to level the
surface. As soon as a contour that
approximates to the correct one is achieved,
stop working the paste - if you carry on too
long, the paste will become sticky and begin
to “pick-up” on the applicator. Continue to
add thin layers of filler paste at 20-minute
intervals, until the level of the filler is just
proud of the surrounding bodywork.
Once the filler has hardened, the excess
can be removed using a metal plane or file.
From then on, progressively-finer grades of
abrasive paper should be used, starting with a
40-grade production paper, and finishing with
a 400-grade wet-and-dry paper. Always wrap
the abrasive paper around a flat rubber, cork,
or wooden block - otherwise the surface of
the filler will not be completely flat. During the
smoothing of the filler surface, the wet-and-
dry paper should be periodically rinsed in
water. This will ensure that a very smooth
finish is imparted to the filler at the final stage.
At this stage, the “dent” should be
surrounded by a ring of bare metal, which in
turn should be encircled by the finely
“feathered” edge of the good paintwork.
Rinse the repair area with clean water, until all
of the dust produced by the rubbing-down
operation has gone.
Spray the whole area with a light coat of
primer - this will show up any imperfections in
the surface of the filler. Repair these
imperfections with fresh filler paste or
bodystopper, and once more smooth the
surface with abrasive paper. Repeat this
spray-and-repair procedure until you are
satisfied that the surface of the filler, and the
feathered edge of the paintwork, are perfect.
Clean the repair area with clean water, and
allow to dry fully.The repair area is now ready for final
spraying. Paint spraying must be carried out
in a warm, dry, windless and dust-free
atmosphere. This condition can be created
artificially if you have access to a large indoor
working area, but if you are forced to work in
the open, you will have to pick your day very
carefully. If you are working indoors, dousing
the floor in the work area with water will help
to settle the dust which would otherwise be in
the atmosphere. If the repair area is confined
to one body panel, mask off the surrounding
panels; this will help to minimise the effects of
a slight mis-match in paint colours. Bodywork
fittings (eg chrome strips, door handles etc)
will also need to be masked off. Use genuine
masking tape, and several thicknesses of
newspaper, for the masking operations.
Before commencing to spray, agitate the
aerosol can thoroughly, then spray a test area
(an old tin, or similar) until the technique is
mastered. Cover the repair area with a thick
coat of primer; the thickness should be built
up using several thin layers of paint, rather
than one thick one. Using 400-grade wet-and-
dry paper, rub down the surface of the primer
until it is really smooth. While doing this, the
work area should be thoroughly doused with
water, and the wet-and-dry paper periodically
rinsed in water. Allow to dry before spraying
on more paint.
Spray on the top coat, again building up the
thickness by using several thin layers of paint.
Start spraying at one edge of the repair area,
and then, using a side-to-side motion, work
until the whole repair area and about 2 inches
of the surrounding original paintwork is
covered. Remove all masking material 10 to
15 minutes after spraying on the final coat of
paint.
Allow the new paint at least two weeks to
harden, then, using a paintwork renovator, or
a very fine cutting paste, blend the edges of
the paint into the existing paintwork. Finally,
apply wax polish.
Plastic components
With the use of more and more plastic body
components by the vehicle manufacturers (eg
bumpers. spoilers, and in some cases major
body panels), rectification of more serious
damage to such items has become a matter
of either entrusting repair work to a specialist
in this field, or renewing complete
components. Repair of such damage by the
DIY owner is not really feasible, owing to the
cost of the equipment and materials required
for effecting such repairs. The basic technique
involves making a groove along the line of the
crack in the plastic, using a rotary burr in a
power drill. The damaged part is then weldedback together, using a hot-air gun to heat up
and fuse a plastic filler rod into the groove.
Any excess plastic is then removed, and the
area rubbed down to a smooth finish. It is
important that a filler rod of the correct plastic
is used, as body components can be made of
a variety of different types (eg polycarbonate,
ABS, polypropylene).
Damage of a less serious nature (abrasions,
minor cracks etc) can be repaired by the DIY
owner using a two-part epoxy filler repair
material. Once mixed in equal proportions,
this is used in similar fashion to the bodywork
filler used on metal panels. The filler is usually
cured in twenty to thirty minutes, ready for
sanding and painting.
If the owner is renewing a complete
component himself, or if he has repaired it
with epoxy filler, he will be left with the
problem of finding a suitable paint for finishing
which is compatible with the type of plastic
used. At one time, the use of a universal paint
was not possible, owing to the complex range
of plastics encountered in body component
applications. Standard paints, generally
speaking, will not bond to plastic or rubber
satisfactorily. However, it is now possible to
obtain a plastic body parts finishing kit which
consists of a pre-primer treatment, a primer
and coloured top coat. Full instructions are
normally supplied with a kit, but basically, the
method of use is to first apply the pre-primer
to the component concerned, and allow it to
dry for up to 30 minutes. Then the primer is
applied, and left to dry for about an hour
before finally applying the special-coloured
top coat. The result is a correctly-coloured
component, where the paint will flex with the
plastic or rubber, a property that standard
paint does not normally possess.
6 Bodywork repair-
major damage
5
1Major damage must be repaired by a
qualified bodywork repair specialist, or
preferably by a BMW dealer. Specialised
equipment is required to do the job properly.
2If the damage is extensive, the bodyshell
must be checked for proper alignment, or the
vehicle’s handling characteristics may be
adversely affected and other components
may wear at an accelerated rate.
3Due to the fact that all of the major body
components (bonnet, wings, etc.) are
separate units, any seriously damaged
components should be replaced with new
ones rather than repaired.
Bodywork and fittings 11•3
11
If bodystopper is used, it can
be mixed with cellulose
thinners to form a really thin
paste which is ideal for filling
small holes
Sometimes bodywork
components can be found in
a scrapyard that specialises
in used vehicle components,
often at a considerable saving over the
cost of new parts.

remove the pin (see illustrations). Be sure to
support the bonnet while doing this.
4Have an assistant hold onto the bonnet on
one side while you hold the other side.
5Remove the bonnet-to-hinge assembly
bolts on your side of the bonnet, then hold
your side of the bonnet while your assistant
removes the bonnet-to-hinge bolts on the
other side.
6Remove the bonnet. Place it somewhere
safe where it will not be knocked over, with
rags to protect the paintwork where it rests on
the ground or against a wall.
7Refitting is the reverse of removal.
5-Series models
8Open the bonnet. On some later models, it
may be necessary to prise out the plastic clips
and remove the insulation pad for access tothe bonnet light connector and windscreen
washer hoses (see illustrations). Having
done this, disconnect the wires and hoses.
9Detach the clips and withdraw the bonnet
support pins (see illustration).
10Remove the pins from the hinges (see
illustration).
11Have an assistant hold onto the bonnet on
one side while you hold the other side.
12Remove the bonnet-to-hinge through-bolt
on your side of the bonnet, then hold your
side of the bonnet while your assistant
removes the through-bolt on the other side
(see illustration).
13Remove the bonnet. Place it somewhere
safe where it will not be knocked over, with
rags to protect the paintwork where it rests on
the ground or against a wall.
14Refitting is the reverse of the removal.
Adjustment
15The bonnet can be adjusted to obtain a
flush fit between the bonnet and wings after
loosening the bonnet hinge bolts. On some 5-
Series models, it will be necessary to remove the
side grille sections for access to the hinge bolts.
16Move the bonnet from side to side, or
front to rear, until the bonnet is properly
aligned with the wings at the front. Tighten the
bolts securely.
17The rear height of the bonnet can be
adjusted by loosening the bolts, and raising or
lowering the catch (see illustration). After
adjustment, tighten the bolts securely.
18Side-to-side adjustment of the bonnet can
be made by loosening the roller guide bolt
nuts, and moving the guide position until it
slides into the catch properly (see illustration).
Bodywork and fittings 11•5
10.8b . . . prise the retainer out10.8a Use a small screwdriver to prise out
the clip pin, then . . .10.3b . . . and pull the hinge pin out while
supporting the bonnet
10.19 Screw the bonnet stops in or out
after making other adjustments10.18 Loosen the bolts (A) and adjust the
roller guide from side to side until it
engages securely in the catch10.17 Loosen the bolts (arrowed) and raise
or lower the catch to adjust the bonnet
height
10.12 Unscrew the hinge through-bolts
(arrowed)10.10 Support the bonnet and withdraw
the pin10.9 Pull off the clip with needle-nose
pliers
11

19After adjustment, screw the stop pads in
or out to support the bonnet in its new
position (see illustration).
20The bonnet mechanism should be
lubricated periodically with grease, to prevent
sticking or jamming.
11 Bumpers-
removal and refitting
1
Removal
1Detach the bumper cover (if applicable) and
where necessary the front spoiler.
2Disconnect any wiring or other components
that would interfere with bumper removal.
3Support the bumper with a jack or axle
stand. Alternatively, have an assistant support
the bumper as the bolts are removed.
4Remove the retaining bolts and detach the
bumper.
Refitting
5Refitting is a reversal of removal. Tighten
the retaining bolts securely, then refit the
bumper cover and any other components that
were removed.
12 Door trim panel-
removal and refitting
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.
Removal
1Disconnect the battery negative cable.
2Remove all door trim panel retaining screws
and door pull/armrest assemblies.3On models with manual (non-electric)
windows, remove the window regulator
handle (see illustration). On models with
electric windows, prise off the control switch
assembly and unplug it.
4Disengage the trim panel-to-door retaining
clips. Work around the outer edge until the
panel is free.
5Once all of the clips are disengaged, detach
the trim panel, unplug any electrical
connectors, and remove the trim panel from
the vehicle.
6For access to the inner door, carefully peel
back the plastic water shield.
Refitting
7Prior to refitting the door trim panel, be sure
to renew any clips in the panel which may
have come out (or got broken) during the
removal procedure.
8Plug in the electrical connectors (where
applicable) and place the panel in position in
the door. Press the door panel into place until
the clips are seated, then refit the
armrest/door pulls. Refit the window regulator
handle, where applicable.
13 Door- removal, refitting and
adjustment
1
Removal
1Remove the door trim panel (see Section
12). Disconnect any electrical connectors, andpush them through the door opening so they
won’t interfere with door removal.
2Place a trolley jack or axle stand under the
door, or have an assistant on hand to support
it when the hinge bolts are removed. Note: If a
jack or axle stand is used, place a rag between
it and the door, to protect the door’s painted
surfaces.
3Scribe or mark around the door hinges.
4Disconnect the door check strap by prising
the circlip out of the end of the pin, then slide
the pin out (see illustration). A roll pin is fitted
to some models; this is removed by driving it
out with a pin punch.
5Remove the hinge-to-door nuts, and
carefully lift off the door (see illustration).
Refitting and adjustment
6Refitting is the reverse of removal.
7Following refitting of the door, check the
alignment and adjust it if necessary as
follows:
a) Up-and-down and fore-and-aft
adjustments are made by loosening the
hinge-to-body nuts and moving the door
as necessary.
b) The door lock striker can also be adjusted
both up and down and sideways, to
provide positive engagement with the lock
mechanism. This is done by loosening the
mounting bolts and moving the striker as
necessary (see illustration).
14 Boot lid/tailgate- removal,
refitting and adjustment
1
Boot lid
1Open the boot lid, and cover the edges of
the boot compartment with pads or cloths to
protect the painted surfaces when the lid is
removed.
2Disconnect any cables or electrical
connectors attached to the boot lid that would
interfere with removal.
3Make alignment marks around the hinge
bolts (see illustration).
4Have an assistant support the lid, then
remove the lid-to-hinge bolts on both sides
and lift it off.
11•6 Bodywork and fittings
13.7 The door lock striker position can be
adjusted after loosening the screws
(arrowed)13.5 Remove the nuts (arrowed) and
detach the door from the hinges
13.4 Detach the circlip (arrowed) from the
tapered end of the pin12.3 On models without electric windows,
prise off the window regulator handle trim
piece for access to the retaining screw

15 Latch, lock cylinder and
handles- removal, refitting
and adjustment
1
1Remove the trim panel(s) and, on the door,
the plastic shield (see Section 12).
Latch
2Disconnect the operating rods from the
latch (see illustration).
3Remove the latch retaining screws.
4Detach the latch assembly and withdraw it.
5Refitting is the reverse of removal.
Lock cylinder
6Detach the linkage.
7Use a screwdriver to slide the retaining clip
off, and withdraw the lock cylinder.
8Refitting is the reverse of removal.
Interior handle
9Disconnect the operating rod from the
handle.
10Remove the retaining screws and lift the
handle from the door.
11Refitting is the reverse of removal.
Exterior handle
12Lift up the handle for access, remove the
two retaining screws, then detach the handle
from the door.
13Refitting is the reverse of removal.
16 Door window glass-
removal and refitting
3
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.
2Remove the door trim panel and the plastic
water shield (see Section 12).
3Prise the door inner and outer weatherstrips
from the door.
Front door
4Raise the window so that the mounting
bolts can be reached through the access hole.
If electric windows are fitted, temporarily
reconnect the battery cable to accomplish
this.
5Support the glass, and remove the retaining
bolts securing the glass to the regulator.
6Lift the window glass up and out of the door
window slot, then tilt it and remove it from the
door.
7Refitting is the reverse of removal.
Rear door
8Carry out the operations described in
paragraphs 1 to 5.
3-Series models
9Disengage the glass from the front guide
roller, and prise out the rubber window
guides.
10Remove the door handle screws, and
allow the handle assembly to hang out of the
way.
11Remove the rear window frame bolts,
push the frame into the door, and remove the
window glass.
12Refitting is the reverse of removal.
5-Series models
13Loosen the rear window guide mounting
bolt.14Detach the glass from the front guide
roller, disengage the glass from the guide
rails, then slide the glass to the rear and
remove by lifting from above.
15The fixed glass can be removed by
removing the guide rail bolts, then pulling the
rail down to the rear and detaching the glass.
16Refitting is the reverse of removal. The
rear window glass can be adjusted by
loosening the adjustment bolts, then raising
the glass to within one inch of the top of the
door opening. Adjust the glass-to-
opening gap evenly, then tighten the bolts
securely.
17 Door window regulator-
removal and refitting
3
Removal
1Remove the door window glass (Sec-
tion 16).
2Remove the securing bolts or nuts, and lift
the window regulator assembly out of the
door (withdraw the regulator mechanism
through the access hole). On models with
electric windows, unplug the electrical
connector.
Refitting
3Refitting is the reverse of removal.
18 Exterior mirror-
removal and refitting
1
Removal
1If it is required to renew the mirror glass
only, insert a small screwdriver through the
hole in the bottom of the exterior mirror, and
carefully lever clockwise the plastic holder on
the rear of the glass (ie move the bottom of
the screwdriver to the right). This will release
the glass, which can then be withdrawn. If
electric mirrors are fitted, it will be necessary
to disconnect the wiring before completely
removing the glass.
2To remove the complete mirror, prise off
the cover panel (and/or the tweeter speaker,
where applicable).
3Unplug the electrical connector.
4Remove the retaining screws and lift the
mirror off
Refitting
5Refitting is the reverse of removal.
11•8 Bodywork and fittings
15.2 Typical door latch, lock cylinder and
handle details
14.14 Unscrewing the hinge mounting
bolts (5-Series)

19 Steering column shrouds -
removal and refitting
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.
Removal
1Disconnect the battery negative cable.
2Remove the steering wheel (Chapter 10).
3Remove the upper shroud screws (see
illustration).
4Remove the two screws from the underside
of the column (see illustration).
5Detach the lower shroud, then lift the upper
half off the column (see illustrations).
Refitting
6Refitting is the reverse of removal.
20 Seats- removal and refitting
1
Front seat
1Remove the four bolts securing the seat
track to the floorpan, and lift the seat from the
vehicle (see illustration). On some models, it
will be necessary to disconnect the seat
heating wiring; it may also be necessary to
detach the seat belt from the seat.2Refitting is the reverse of removal. Tighten
the retaining bolts securely.
Rear seat cushion
3If applicable, first remove the two retaining
bolts. Grasp the front of the cushion
(Saloon/Convertible models) or the rear of the
cushion (Touring/Estate models) securely, and
pull up sharply (see illustration).
4Refitting is the reverse of the removal.
21 Seat belt check
1
1Check the seat belts, buckles, lock plates
and guide loops for obvious damage and
signs of wear.
2Where applicable, check that the seat belt
reminder light comes on when the ignition key
is turned to the Run or Start position.
3The seat belts are designed to lock up
during a sudden stop or impact, yet allow free
movement during normal driving. Check thatthe retractors return the belt against your
chest while driving and rewind the belt fully
when the buckle is unlocked.
4If any of the above checks reveal problems
with the seat belt system, renew parts as
necessary.
5Belts which have been subject to impact
loads must be renewed.
Bodywork and fittings 11•9
19.5a Pull the tilt lever down (where fitted),
and lower the shroud from the steering
column19.4 The lower screws are located under
the tilt lever (where fitted)19.3 Use a Phillips screwdriver to remove
the upper column shroud screws
20.3 Grasp the seat at the front edge and
pull up sharply (Saloon/Convertible
models)20.1 The front seats are held in place by
bolts (arrowed)
19.5b Rotate the upper shroud up and off
the steering column
11

Finding a short-circuit
One method of finding a short-circuit is to
remove the fuse and connect a test light or
voltmeter in its place. There should be no
voltage present in the circuit. Move the
electrical connectors from side-to-side while
watching the test light. If the bulb goes on,
there is a short to earth somewhere in that
area, probably where the insulation has been
rubbed through. The same test can be
performed on each component in a circuit,
even a switch.
Earth check
Perform a earth check to see whether a
component is properly earthed (passing
current back via the vehicle body). Disconnect
the battery, and connect one lead of a self-
powered test light (often known as a
continuity tester) to a known good earth.
Connect the other lead to the wire or earth
connection being tested. The bulb should
light, indicating a good earth connection. If
not, dismantle the connection, and clean all
relevant parts thoroughly. When re-making
the connection, use serrated (shakeproof)
washers if possible, and tighten all bolts, etc,
securely.
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.
Continuity check
A continuity check determines if there are
any breaks in a circuit - if it is conducting
electricity properly. With the circuit off (no
power in the circuit), a self-powered continuity
tester can be used to check the circuit.
Connect the test leads to both ends of the
circuit, and if the test light comes on, the
circuit is passing current properly. If the light
doesn’t come on, there is a break somewhere
in the circuit. The same procedure can be
used to test a switch, by connecting the
continuity tester to the power-in and power-
out sides of the switch. With the switch turned
on, the test light should come on.
Finding an open-circuit
When diagnosing for possible open-
circuits, it is often difficult to locate them by
sight, because oxidation or terminal
misalignment are hidden by the connectors.
Intermittent problems are often caused by
oxidised or loose connections. Merely
wiggling an electrical connector may correct
the open-circuit condition, albeit temporarily.
Dismantle the connector, and spray with a
water-dispersant aerosol. On simpler
connectors, it may be possible to carefullybend the connector pins inside, to improve
the metal-to-metal contact - don’t damage
the connector in the process, however.
3 Fuses- general information
1
The electrical circuits of the vehicle are
protected by a combination of fuses and
circuit breakers. The fusebox is located in the
left corner of the engine compartment (see
illustration). On some later models, it is
located under the rear seat cushion.
Each of the fuses is designed to protect a
specific circuit, and on some models, the
various circuits are identified on the fuse
panel itself.
Miniaturised fuses are employed in the
fuseboxes. These compact fuses, with blade
terminal design, allow fingertip removal and
renewal. If an electrical component fails,
always check the fuse first. A blown fuse is
easily identified through the clear plastic
body. Visually inspect the element for
evidence of damage. If a continuity check is
called for, the blade terminal tips are exposed
in the fuse body.
Be sure to renew blown fuses with the
correct type. Fuses of different ratings are
physically interchangeable, but only fuses of
the proper rating should be used. Replacing a
fuse with one of a higher or lower value than
specified is not recommended. Each electrical
circuit needs a specific amount of protection.
The amperage value of each fuse is moulded
into the fuse body.
If the new fuse immediately fails, don’t
renew it again until the cause of the problem
is isolated and corrected. In most cases, the
cause will be a short-circuit in the wiring
caused by a broken or deteriorated wire.
4 Relays- general information
1
Several electrical accessories in the vehicle
use relays to transmit the electrical signal to
the component. If the relay is defective, thatcomponent will not operate properly. Relays
are electrically-operated switches, which are
often used in circuits drawing high levels of
current, or where more complex switching
arrangements are required.
The various relays are grouped together for
convenience in several locations under the
dash and in the engine compartment (see
accompanying illustration and illus-
tration 3.1).
If a faulty relay is suspected, it can be
removed and tested by a dealer or qualified
automotive electrician. No overhaul is
possible. Like fuses, defective relays must be
replaced with the correct type; some relays
look identical, but perform very different
functions.
5 Direction indicator/hazard
warning flasher unit- check
and renewal
2
Warning: Some later models are
equipped with an airbag or
Supplemental Restraint System
(SRS). To avoid possible damage
to this system, the manufacturer
recommends that, on airbag-equipped
models, the following procedure should be
left to a dealer service department, or
other specialist, because of the special
tools and techniques required. There is a
risk of injury if the airbag is accidentally
triggered.
1The direction indicator/hazard flasher unit is
a small canister- or box-shaped unit located
in the wiring harness on or near the steering
column. Access is gained by removing the
steering column shrouds (see illustration).
2When the flasher unit is functioning
properly, a regular clicking noise can be heard
from it when the indicators or hazard flashers
are switched on. If the direction indicators fail
on one side or the other, and the flasher unit
does not make its characteristic clicking
sound, a faulty direction indicator bulb is
indicated.
3If both direction indicators fail to blink, the
problem may be due to a blown fuse, a faulty
flasher unit, a broken switch or a loose or open
connection. If a quick check of the fusebox
12•2 Body electrical systems
4.2 Engine compartment relays3.1 The fusebox is located in the engine
compartment under a cover - the box also
includes several relays

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.

12Refitting is a reversal of removal. When
fitting the motor, if necessary plug in the
connector and run the motor briefly until it is
in the “neutral” (wiper parked) position.
17 Heated rear window-
check and repair
2
1The heated rear window consists of a
number of horizontal elements on the glass
surface.
2Small breaks in the element can be repaired
without removing the rear window.
Check
3Switch on the ignition and the heated rear
window.
4Place the positive lead of a voltmeter to the
heater element nearest to the incoming power
source.
5Wrap a piece of aluminium foil around the
negative lead of the voltmeter on the positive
side of the suspected broken element, and
slide it slowly towards the negative side.
Watch the voltmeter needle - when it moves
from zero, you have located the break.
Repair
6Repair the break in the line using a repair kit
recommended specifically for this purpose,
such as BMW repair kit No. 81 22 9 (or
equivalent). Included in this kit is plastic
conductive epoxy. The following paragraphs
give general instructions for this type of repair;
follow the instructions supplied with the repair
kit if they are different.
7Prior to repairing a break, switch off the
circuit and allow it to cool down for a few
minutes.
8Lightly buff the element area with fine steel
wool, then clean it thoroughly.
9Use masking tape to mask off the area of
repair, leaving a slit to which the epoxy can be
applied.
10Mix the epoxy thoroughly, according to
the instructions on the package.
11Apply the epoxy material to the slit in the
masking tape, overlapping the undamaged
area about 20 mm on each end.12Allow the repair to cure for 24 hours
before removing the tape and using the
heated rear window.
18 Supplemental Restraint
System (SRS)- general
information
Later models are equipped with a
Supplemental Restraint System (SRS),
incorporating an airbag. This system is
designed to protect the driver from serious
injury in the event of a head-on or frontal
collision. It consists of an airbag module in the
centre of the steering wheel, two crash
sensors mounted on the front inner wing
panels, and a crash safety switch located
inside the passenger compartment.
The airbag module contains a housing
incorporating the airbag and the inflator units.
The inflator assembly is mounted on the back
of the housing over a hole through which gas
is expelled, inflating the bag almost instanta-
neously when an electrical signal is sent from
the system. This signal is carried by a wire
which is specially wound with several turns,
so the signal will be transmitted regardless of
the steering wheel position.
The SRS system has three sensors: two at
the front, mounted on the inner wing panels
(see illustration), and a safety switch located
inside the passenger compartment. The crash
sensors are basically pressure-sensitive
switches, which complete an electrical circuit
during an impact of sufficient force. The
electrical signal from the crash sensors is sent
to a third sensor, which then completes the
circuit and inflates the airbag.
The module containing the safety switch
monitors the system operation. It checks the
system every time the vehicle is started,
causing the AIRBAG warning light to come on,
then go out if the system is operating
correctly. If there is a fault in the system, the
light will stay on. If the AIRBAG warning light
does stay on, or if it comes on while driving,
take the vehicle to your dealer immediately.
19 Cruise control system-
description and check
1
The cruise control system maintains vehicle
speed using a vacuum-actuated servo motor
located in the engine compartment, which is
connected to the throttle linkage by a cable.
The system consists of the servo motor,
clutch switch, brake switch, control switches,
a relay, and associated vacuum hoses.
Because of the complexity of the cruise
control system, repair should be left to a
dealer service department. However, it is
possible for the home mechanic to make
simple checks of the wiring and vacuum
connections for minor faults which can be
easily repaired. These include:
a) Inspect the cruise control actuating switches
for broken wires and loose connections.
b) Check the cruise control fuse.
c) The cruise control system is operated by
vacuum, so it’s critical that all vacuum
switches, hoses and connections are
secure. Check the hoses in the engine
compartment for loose connections,
cracks, or obvious vacuum leaks.
20 Central locking system-
description and check
2
The central door locking system operates
the door lock actuators mounted in each
door. The system consists of the switches,
actuators and associated wiring. Diagnosis is
limited to simple checks of the wiring
connections and actuators for minor faults
which can be easily repaired. These include:
a) Check the system fuse and/or circuit
breaker (where applicable).
b) Check the switch wires for damage and
loose connections. Check the switches
for continuity.
c) Remove the door trim panel(s), and check
the actuator wiring connections to see if
they’re loose or damaged. Inspect the
actuator rods to make sure they aren’t
12•8 Body electrical systems
18.3 The SRS system crash sensors
(arrowed) are located in the engine
compartment - check the wiring regularly
for damage16.11b Tailgate wiper motor (5-Series)16.11c Wiper blade and pivot mechanism
on the rear window (5-Series)