1988 OPEL CALIBRA Service Repair Manual

4If adjustment is necessary, release the
clamp screw and turn the cam plate in the
desired direction. Tighten the clamp screw,
and recheck the pump delivery (see
illustration).
Removal
5Proceed as described in Section 17,
paragraphs 1 and 2.
6Thoroughly clean all external dirt from the
area around the accelerator pump housing.
7Remove the four securing screws and lift off
the accelerator pump cover. Recover the
diaphragm, spring, valve retainer and valve.
Note the orientation of the valve retainer.
Refitting
8Clean the mating faces of the cover and
housing.
9Check the condition of the valve, and renew
if necessary.
10Begin refitting by locating the valve, valve
retainer and spring in the housing. Note that
the valve retainer can only be fitted in one
position. The larger diameter of the spring
should rest against the valve retainer.
11Locate the diaphragm on the housing,
ensuring that the spring is correctly seated,
and refit the cover. Tighten the cover securing
screws progressively to avoid distorting the
diaphragm (see illustration).
12Further refitting is a reversal of removal.
19Automatic choke unit -
removal, refitting and
adjustment
3
Note: Refer to Section 2 before proceeding. A
tachometer and an exhaust gas analyser will
be required to check the idle speed and
mixture on completion. If the coolant housing
is removed, new O-rings will be required for
refitting
Removal
1Proceed as described in Section 17,
paragraphs 1 and 2.
2Note the position of the bi-metal housing
alignment marks as an aid to refitting, if
necessary making additional marks for clarity,
then remove the three securing screws and lift
off the bi-metal housing. Place the housing to
one side, taking care not to strain the coolant
hoses or electric choke heater wiring.
3Remove the three screws securing the
choke housing to the carburettor body, and
withdraw the choke assembly, taking care not
to bend the choke operating rod.
4If it is necessary to remove the bi-metal
housing for renewal, continue as follows;
otherwise go on to paragraph 8.
5Identify the automatic choke coolant hose
locations as an aid to refitting, then
disconnect the hoses. Be prepared for
coolant spillage, and either plug the hoses, or
secure them with their ends facing upwards,
to prevent further loss of coolant.
6Disconnect the wiring from the electric
choke heater, and withdraw the bi-metal
housing.
7The coolant housing can be separated from
the bi-metal housing by unscrewing the
central securing bolt. Recover the O-rings
from under the bolt head, and from the rim of
the coolant housing.
Refitting
8Begin refitting by locating the choke
assembly on the carburettor body, ensuring
that the lever on the choke assembly engages
with the choke operating rod. Tighten the
three securing screws.
9Check and if necessary adjust the choke
valve gap and the fast idle cam position, as
described in paragraphs 15 to 19, of this
Section.10Connect the bi-metal spring to the choke
lever, position the bi-metal housing on the
choke housing, and loosely fit the securing
screws. Align the marks on the bi-metal
housing and the choke housing as noted
during removal, then tighten the securing
screws.
11Where applicable, refit the coolant
housing to the bi-metal housing, using new O-
rings if necessary, and reconnect the coolant
hoses and electric choke heater wiring.
12Further refitting is a reversal of removal,
remembering the following points.
13If the coolant hoses have been
disconnected, check the coolant level, as
described in Chapter 3.
14Check and if necessary adjust the fast idle
speed, as described in paragraphs 25 to 34,
of this Section.
Adjustment
Choke valve gap
15With the bi-metal housing removed as
described in paragraphs 2 to 4, of this
Section, continue as follows.
16Press the choke operating lever fully
clockwise, and retain it in position with a
rubber band.
17Move the throttle lever to the fully open
position, and measure the choke valve gap
between the lower side of the choke plate and
the wall of the primary barrel. Check that the
gap is as given in the Specifications.
18If necessary, adjust the choke valve gap
by bending the “adjuster segment (2)” If the
gap is too small, enlarge gap “B”, by levering
with a screwdriver. If the gap is too large,
decrease gap “B” using a pair of pliers (see
illustration).
19If no further adjustments are to be carried
out, refit the bi-metal housing, as described in
paragraphs 10 to 14, of this Section.
Fuel and exhaust systems - carburettor models 4A•9
18.11 Carburettor accelerator pump components
1 Cover with operating lever
2 Diaphragm
3 Spring4 Valve
5 Air passage
18.4 Accelerator pump delivery adjustment: “+” to
increase, “-” to reduce
4A

Fast idle cam position
20With the bi-metal housing removed, and
the choke valve gap “B”, correctly set,
continue as follows.
21Open the throttle valve, then close the
choke valve using light finger pressure on the
choke drive lever (see illustration). Close the
throttle valve.
22Check that the fast idle speed adjustment
screw is resting against the stop on the
second highest step of the fast idle cam.
23If adjustment is required, first check that
the choke return spring is correctly
positioned, then adjust by bending the
adjustment lever.
24Refit the bi-metal housing, as described in
paragraphs 10 to 14 of this Section.
Fast idle speed
Note: To carry out the adjustment, an
accurate tachometer and an exhaust gas
analyser (CO meter) will be required
25Check the idle speed and mixture, as
described in Section 14. The idle speed must
be correct before attempting to check or
adjust the fast idle speed.
26With the engine at normal operating
temperature, and a tachometer connected
according to the equipment manufacturer’s
instructions, continue as follows.
27Position the fast idle speed adjustment
screw on the second highest step of the fast
idle cam (see illustration).
28Start the engine without touching the
throttle pedal, and check that the fast idle
speed is as specified. If adjustment is
required, stop the engine and continue as
follows.29Remove the tamperproof cap from the
fast idle speed adjustment screw, ensure that
no local or national laws are being broken by
doing so (see illustration).
30Ensure that the adjustment screw is still
resting on the second highest step of the fast
idle cam, then start the engine, again without
touching the throttle pedal.
31Turn the adjustment screw using a
screwdriver, until the specified fast idle speed
is obtained.
32If the cooling fan cuts in during the
adjustment procedure, stop the adjustments,
and continue when the cooling fan stops.
33On completion of adjustment, stop the
engine and disconnect the tachometer.
34Fit a new tamperproof cap to the fast idle
speed adjustment screw, where this is
required by law.
20Automatic choke vacuum
pull-down units - removal,
refitting and adjustment
3
Main diaphragm unit
Note: Refer to Section 2 before proceeding. A
new star clip must be used when refitting the
diaphragm unit. Test vacuum units as
described in Section 16, paragraph 1.
Removal
1Proceed as described in Section 17,
paragraphs 1 and 2.
2Disconnect the diaphragm unit vacuum
pipes.
3Using a pin punch, tap out the roll pin
securing the diaphragm unit to the carburettor
top cover.
4Note the position of the bi-metal housing
alignment marks as an aid to refitting, if
necessary making additional marks for clarity,
then remove the three securing screws, and
lift off the bi-metal housing. Place the housing
to one side, taking care not to strain the
coolant hoses or electric choke heater wiring.
4A•10Fuel and exhaust systems - carburettor models
19.18 Choke valve gap adjustment
1 Choke operating lever
2 Adjuster segment
B Choke valve gap
19.21 Fast idle cam adjustment
1 Fast idle cam
2 Adjustment lever
3 Choke drive lever
4 Fast idle speed adjustment screw
19.29 Tamperproof cap (arrowed) fast idle speed adjustment
screw19.27 Fast idle speed adjustment
3 Fast idle speed adjustment screw
4 Screw positioned on second highest step of cam

5Remove the three screws securing the
choke assembly to the carburettor body.
Allow the choke assembly to drop down, but
do not disconnect the choke linkage.
6Remove the star clip that secures the
diaphragm unit to the carburettor top cover,
and withdraw the diaphragm unit.
Refitting
7Refitting is a reversal of removal, but use a
new star clip to secure the diaphragm unit to
the carburettor top cover. Before refitting the
air box to the top of the carburettor, check
and if necessary adjust the choke pull-down,
as follows.
Vacuum pull-down
Adjustment
8With the air cleaner or air box removed from
the top of the carburettor, as described in
Section 17, paragraph 2, continue as follows.
9Note the position of the bi-metal housing
alignment marks as an aid to refitting, if
necessary making additional marks for clarity,
then remove the three securing screws, and
lift off the bi-metal housing. Place the housing
to one side, taking care not to strain the
coolant hoses or electric choke heater wiring.
10Position the fast idle speed adjustment
screw on the highest step of the fast idle cam,
and check that the choke valve is closed.
11Move the pull-down arm towards the
diaphragm unit by pushing on the adjustment
screw until resistance is felt. Hold the arm in
this position.
12Using a drill shank of appropriate
diameter, or a similar item, measure the
clearance between the lower side of the
choke plate and the wall of the primary barrel
(see illustrations). Check that the clearance
is as given for the “small” choke pull-down
gap in the Specifications.
13If adjustment is necessary, turn the
adjustment screw in the appropriate direction,
using an Allen key, until the clearance is
correct.14Now push the pull-down arm towards the
diaphragm unit as far as its stop, and hold the
arm in this position.
15As before measure the clearance between
the lower side of the choke plate and the wall
of the primary barrel. Check that the
clearance is as given for the “large” choke
pull-down gap in the Specifications.
16If adjustment is necessary, turn the
adjustment screw in the appropriate direction
until the clearance is correct.
17Connect the bi-metal spring to the choke
lever, position the bi-metal housing on the
choke housing and loosely fit the securing
screws. Align the marks on the bi-metal
housing and the choke housing as noted
during removal, then tighten the securing
screws.
18Refit the air box to the top of the
carburettor on completion.
Secondary pull-down solenoid
Removal
19This unit operates in conjunction with the
main diaphragm unit.
20To remove the solenoid unit, first continue
as described in Section 17, paragraphs 1 and
2.
21Disconnect the diaphragm unit vacuum
pipe.22Disconnect the wiring plug, then unscrew
the securing screw, and withdraw the
solenoid unit and its mounting bracket from
the carburettor. Note that the securing screw
also secures the wiring plug earth lead (see
illustration).
Refitting
23Refitting is a reversal of removal, but
ensure that the wiring plug earth lead is in
place under the solenoid bracket securing
screw.
21Carburettor filter -removal
and refitting
3
Removal
1A small tubular filter gauze is fitted into the
carburettor top cover’s fuel inlet union to
remove any particles of dirt from the fuel.
2To ensure a clean fuel supply and to
prevent the risk of misfiring, poor starting or
other problems due to a restricted fuel supply,
this filter must be cleaned and/or renewed at
the interval specified in Chapter 1.
3To reach the filter, remove the air cleaner or
air box, as applicable, then disconnect and
plug the hose from the fuel pump or vapour
separator to the top cover union.
4Remove the filter by hooking it out with a
small screwdriver, or by snaring it with a long
thin screw (3 mm thread size, screwed
approximately 5 mm into the filter).
5If the filter is blocked or heavily fouled, or if
it is torn, distorted or damaged in any way, it
must be renewed. If it is fit for further use,
clean it using a jet of compressed air or by
brushing away particles of dirt with an old soft
toothbrush. Then flushing it in clean solvent,
taking care not to allow any overspray to get
into your eyes; if petrol is used, take care to
prevent the risk of fire.
Fuel and exhaust systems - carburettor models 4A•11
20.12B Checking the vacuum pull-down gap using a twist drill
20.22 Secondary choke pull-down
solenoid securing screw and earth lead
20.12A Choke vacuum pull-down adjustment
1 Adjustment screw 2 Diaphragm unit A Twist drill
4A

Refitting
6On refitting the filter, press it into the union
until it catches (see illustration). The
remainder of the reassembly procedure is the
reverse of removal.
22Throttle valve dashpot
(automatic models) -
adjustment
2
1Remove the air cleaner or air box, refer to
Section 3.
2Ensure that the lever (see illustration)is in
the idling position.
3Slacken the locknut and unscrew the
dashpot until a gap of 0.05 mm (0.002 in)
exists between the lever and the dashpot tip.
Then screw the dashpot downwards 2.5 full
turns and tighten the locknut.
4Refit all removed components.
23Throttle position sensor
(automatic transmission
models) - removal and refitting
2
Removal
1Disconnect the battery earth lead.
2Disconnect the wiring plug from the sensor.
3Either unscrew the two securing screws
and withdraw the sensor from its bracket, or
unbolt the bracket.
Refitting
4Refitting is the reverse of the removal
procedure, noting the following points.
a)Install the sensor when the throttle valve
is fully closed and ensure that the
adapter, “1” (see illustration),seats
correctly on the throttle valve spindle.
b)Tighten the screws carefully.
24Idle speed increase valve -
testing
2
1Certain models are fitted with an idle speed
increase valve that is attached to the side of
the carburettor.
2To test the operation of this valve first
remove the air filter and vacuum hose.
3With the valve’s plug connected, have
someone turn the ignition on (but do not start
the engine). A mechanical shifting noise
should be heard. If not replace the unit.
4After refitting replace the vacuum hose and
air filter.
25Idle cut-off solenoid (1.8 litre
models) - description and
testing
2
Note: Refer to Section 2 before proceeding
Description
1On 1.8 litre models, the carburettor is fitted
with an idle cut-off solenoid. This is an
electrically operated valve, which interrupts
the idle mixture circuit when the ignition isswitched off, thus preventing the engine from
running-on (see illustration).
2The idle cut-off solenoid is energised all the
time that the ignition is switched on. A
defective solenoid, or a break in its power
supply, will cause the engine to stall or idle
roughly, although it will run normally at speed.
Testing
3If the operation of the solenoid is suspect,
first check that battery voltage is present at
the solenoid terminal when the ignition is
switched on. Use a 12 volt test lamp or similar
test device.
4If no voltage is present, then the fault lies in
the wiring to the solenoid. If voltage is
present, the solenoid can be tested as
follows.
5With the solenoid unscrewed from the
carburettor, connect the body of the solenoid
to the negative terminal of a 12 volt battery.
When the battery positive terminal is
connected to the solenoid centre terminal,
there should be an audible click, and the
needle at the tip of the solenoid should
retract.
6A defective idle cut-off solenoid must be
renewed.
26Inlet manifold - removal and
refitting
3
Note: Refer to Section 2 before proceeding. A
new manifold gasket must be used on refitting
Removal
1Disconnect the battery negative lead.
2Drain the cooling system, as described in
Chapter 3.
3Proceed as described in Section 13,
paragraphs 2 to 7 inclusive, ignoring the
reference to coolant spillage in paragraph 5.
4A•12Fuel and exhaust systems - carburettor models
21.6 Refitting the carburettor fuel filter
23.4 Throttle position sensor - models with automatic
transmission
1 Adapter 2 Sensor22.2 Adjusting the throttle valve dashpot - models with
automatic transmission
1 Lever2 Locknut3 Dashpot

4Disconnect the coolant hose from the rear
of the manifold (see illustration).
5Where applicable, disconnect the camshaft
cover breather hose from the rear of the
manifold (see illustration).
6Unscrew the union and disconnect the
brake servo vacuum hose from the manifold.
7On 1.4 and 1.6 litre models, disconnect the
wiring from the temperature gauge sender.
8Unscrew and remove the top alternator
mounting nut and bolt.
9On 1.4 and 1.6 litre models, disconnect and
remove the stub hose that connects the
crankcase breather tube to the rear of the
camshaft housing.
10Make a final check to ensure that all
relevant hoses, pipes and wires have been
disconnected.
11Unscrew the securing nuts, and withdraw
the manifold from the cylinder head (see
illustration). Note the position of the rear
engine lifting bracket, which is secured by one
of the manifold nuts, and recover the manifoldgasket.
12It is possible that some of the manifold
studs may be unscrewed from the cylinder
head when the manifold securing nuts are
unscrewed. In this event, the studs should be
screwed back into the cylinder head once the
manifold has been removed, using two
manifold nuts locked together.
13If desired, the carburettor can be removed
from the manifold, referring to Section 13, if
necessary.
Refitting
14Refitting is a reversal of removal,
remembering the following points.
15If the carburettor has been removed from
the manifold, refit it, using a new gasket.
16If the alternator mounting bracket has
been unbolted from the manifold, refit it
before refitting the manifold, as access to the
securing bolt is extremely limited once the
manifold is in place.
17Refit the manifold using a new gasket,and ensure that the engine lifting bracket is in
place under the relevant manifold nut. Tighten
the nuts to the specified torque.
18Ensure that all relevant hoses, pipes and
wires are correctly reconnected.
19Refill the cooling system, as described in
Chapter 3.
20Check the throttle cable free play and
adjust if necessary, as described in Section
11.
21If the carburettor has been disturbed,
check and if necessary adjust the idle speed
and mixture, as described in Section 14.
Fuel and exhaust systems - carburettor models 4A•13
26.5 . . .and the camshaft cover breather
hose (arrowed) from the inlet manifold -
1.6 litre model
26.11 Withdrawing the inlet manifold -
1.6 litre model
26.4 Disconnecting the coolant hose . . .
4A
25.1 Carburettor idle cut-off solenoid
(arrowed) - 1.8 litre models

4A•14Notes

12
Wiper blades
Type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 ins. Champion X-4803
Fuses
Rating:
Red . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 A
Blue . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 A
Yellow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 A
Green . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 A
Torque wrench settingsNm lbf ft
Airbag unit to steering wheel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 7
Airbag control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 7
Brackets, passenger airbag . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 16
Passenger airbag to bracket . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 6
Steering to column . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 18
Chapter 12
Body electrical systems
Aerial - removal and refitting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .47
Aerial mast, electric - removal and refitting . . . . . . . . . . . . . . . . . . . .48
Airbag - general . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .55
Airbag contact unit - removal and refitting . . . . . . . . . . . . . . . . . . . . .58
Airbag control unit - removal and refitting . . . . . . . . . . . . . . . . . . . . .61
Airbag unit, drivers side - removal and refitting . . . . . . . . . . . . . . . . .56
Airbag unit, passengers side - removal and refitting . . . . . . . . . . . . .59
Anti-theft alarm - general . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .53
Anti-theft alarm system components - removal and refitting . . . . . . .54
Bracket, passenger airbag unit - removal and refitting . . . . . . . . . . .60
Brake lamp switch - removal and refitting . . . . . . . . . . . . . . . . . . . . .12
Central door locking components - removal and refitting . . . . . . . . .46
Check control system components - removal and refitting . . . . . . . .21
Cigarette lighter - removal and refitting . . . . . . . . . . . . . . . . . . . . . . .15
Clock - removal and refitting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16
Courtesy lamp switch - removal and refitting . . . . . . . . . . . . . . . . . . .10
Direction indicator/lighting switch - removal and refitting . . . . . . . . . .5
Electric door mirror switch - removal and refitting . . . . . . . . . . . . . . . .8
Electric window components - removal and refitting . . . . . . . . . . . . .44
Electric window controls - programming . . . . . . . . . . . . . . . . . . . . . .45
Electrical fault-finding - general information . . . . . . . . . . . . . . . . . . . . .2
Exterior lamp bulbs - renewal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .34
Facia panel switches - removal and refitting . . . . . . . . . . . . . . . . . . . .7
Front indicator lamp unit - removal and refitting . . . . . . . . . . . . . . . .29
Front foglamp - removal, refitting and adjustment . . . . . . . . . . . . . . .31
Fuses and relays - general . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3
General information and precautions . . . . . . . . . . . . . . . . . . . . . . . . . .1
Handbrake “on” warning lamp switch - removal and refitting . . . . . .13
Headlamp aim adjustment motor - removal and refitting . . . . . . . . . .26
Headlamp dim-dip system - general, removal and refitting . . . . . . . .28
Headlamp unit - removal and refitting . . . . . . . . . . . . . . . . . . . . . . . .25
Headlamp washer fluid non-return valve - removal and refitting . . . .43Headlamp wiper motor - removal and refitting . . . . . . . . . . . . . . . . . .40
Headlamps - alignment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .27
Heated front seats - general . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17
Horn(s) - removal and refitting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .22
Ignition switch and lock cylinder - removal and refitting . . . . . . . . . . .4
Instrument panel - removal and refitting . . . . . . . . . . . . . . . . . . . . . .18
Instrument panel components - removal and refitting . . . . . . . . . . . .19
Interior lamp bulbs - renewal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24
Interior lamps - removal and refitting . . . . . . . . . . . . . . . . . . . . . . . . .23
Luggage compartment lamp switch - removal and refitting . . . . . . .11
Number plate lamp - removal and refitting . . . . . . . . . . . . . . . . . . . . .33
Oil pressure warning lamp switch - removal and refitting . . . . . . . . .14
Radio/cassette player - removal and refitting . . . . . . . . . . . . . . . . . . .50
Rear lamp unit - removal and refitting . . . . . . . . . . . . . . . . . . . . . . . .32
Reversing lamp switch . . . . . . . . . . . . . . . . . . . . . . . . .See Chapter 7A
Side repeater lamp - removal and refitting . . . . . . . . . . . . . . . . . . . . .30
Speakers - removal and refitting . . . . . . . . . . . . . . . . . . . . . . . . . . . .49
Speedometer cable - removal and refitting . . . . . . . . . . . . . . . . . . . .52
Steering wheel (with airbag) - removal and refitting . . . . . . . . . . . . . .57
Sunroof motor - removal and refitting . . . . . . . . . . . . . . . . . . . . . . . .51
Sunroof operating switch - removal and refitting . . . . . . . . . . . . . . . . .9
Tailgate wiper motor - removal and refitting . . . . . . . . . . . . . . . . . . . .39
Trip computer components - removal and refitting . . . . . . . . . . . . . .20
Wash/wipe switch - removal and refitting . . . . . . . . . . . . . . . . . . . . . .6
Washer fluid reservoir - removal and refitting . . . . . . . . . . . . . . . . . . .41
Washer nozzles - removal and refitting . . . . . . . . . . . . . . . . . . . . . . .37
Washer pump - removal and refitting . . . . . . . . . . . . . . . . . . . . . . . . .42
Windscreen wiper motor and linkage - removal and refitting . . . . . . .38
Wiper arms - removal and refitting . . . . . . . . . . . . . . . . . . . . . . . . . . .36
Wiper blades - renewal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .35
Wiring diagrams - general . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .62
12•1
Specifications Contents
Easy,suitable for
novice with little
experienceFairly easy,suitable
for beginner with
some experienceFairly difficult,
suitable for competent
DIY mechanic
Difficult,suitable for
experienced DIY
mechanicVery difficult,
suitable for expert DIY
or professional
Degrees of difficulty
54321

1General information and
precautions
The electrical system is of 12-volt negative
earth type. Power for the lights and all
electrical accessories is supplied by a
lead/acid type battery, which is charged by
the alternator.
This Chapter covers repair and service
procedures for the various electrical
components not associated with engine.
Information on the battery, alternator and
starter motor can be found in Chapter 5.
It should be noted that, before working on
any component in the electrical system, the
battery negative terminal should first be
disconnected, to prevent the possibility of
electrical short-circuits and/or fires.
Whenever the occasion arises, carefully
check the routing of the wiring harness,
ensuring that it is correctly secured by the
clips or ties provided so that it cannot chafe
against other components. Carefully check
points such as the clutch cable bracket,
clutch housing and harness support bracket,
the inlet manifold, the horn mounting bracket,
the starter motor terminals, and the rear
bumper and number plate lamp.
If evidence is found of the harness having
chafed against other components, repair the
damage and ensure that the harness is
secured or protected so that the problem
cannot occur again.
2Electrical fault-finding -
general information
Note:Refer to the precautions given in “Safety
first!” (at the beginning of this manual) and to
Section 1 of this Chapter before starting work.
The following tests relate to testing of the main
electrical circuits, and should not be used to
test delicate electronic circuits (such as anti-
lock braking systems), particularly where an
electronic control module is used.
A typical electrical circuit consists of an
electrical component, any switches, relays,
motors, fuses, fusible links or circuit breakers
related to that component, and the wiring and
connectors that link the component to boththe battery and the chassis. To help to
pinpoint a problem in an electrical circuit,
wiring diagrams are included at the end of this
Chapter.
Before attempting to diagnose an electrical
fault, first study the appropriate wiring
diagram, to obtain a complete understanding
of the components included in the particular
circuit concerned. The possible sources of a
fault can be narrowed down by noting
whether other components related to the
circuit are operating properly. If several
components or circuits fail at one time, the
problem is likely to be related to a shared fuse
or earth connection.
Electrical problems usually stem from
simple causes, such as loose or corroded
connections, a faulty earth connection, a
blown fuse, a melted fusible link, or a faulty
relay (refer to Section 3 for details of testing
relays). Visually inspect the condition of all
fuses, wires and connections in a problem
circuit before testing the components. Use
the wiring diagrams to determine which
terminal connections will need to be checked,
to pinpoint the trouble-spot.
The basic tools required for electrical fault-
finding include the following:
a)a circuit tester or voltmeter (a 12-volt bulb
with a set of test leads can also be used
for certain tests).
b)a self-powered test light (sometimes
known as a continuity tester).
c)an ohmmeter (to measure resistance).
d)a battery.
e)a set of test leads.
f)a jumper wire, preferably with a circuit
breaker or fuse incorporated, which can
be used to bypass suspect wires or
electrical components.
Before attempting to locate a problem with
test instruments, use the wiring diagram to
determine where to make the connections.
To find the source of an intermittent wiring
fault (usually due to a poor or dirty
connection, or damaged wiring insulation), a
“wiggle” test can be performed on the wiring.
This involves wiggling the wiring by hand, to
see if the fault occurs as the wiring is moved.
It should be possible to narrow down the
source of the fault to a particular section of
wiring. This method of testing can be used in
conjunction with any of the tests described in
the following sub-Sections.
Apart from problems due to poor
connections, two basic types of fault can
occur in an electrical circuit - open-circuit, or
short-circuit.
Open-circuit faults are caused by a break
somewhere in the circuit, which prevents
current from flowing. An open-circuit fault will
prevent a component from working, but will
not cause the relevant circuit fuse to blow.
Short-circuit faults are caused by a “short”
somewhere in the circuit, which allows the
current flowing in the circuit to “escape” along
an alternative route, usually to earth. Short-
circuit faults are normally caused by abreakdown in wiring insulation, which allows a
feed wire to touch either another wire, or an
earthed component such as the bodyshell. A
short-circuit fault will normally cause the
relevant circuit fuse to blow.
Finding an open-circuit
To check for an open-circuit, connect one
lead of a circuit tester or voltmeter to either
the negative battery terminal or a known good
earth.
Connect the other lead to a connector in
the circuit being tested, preferably nearest to
the battery or fuse.
Switch on the circuit, remembering that
some circuits are live only when the ignition
switch is moved to a particular position.
If voltage is present (indicated either by the
tester bulb lighting or a voltmeter reading, as
applicable), this means that the section of the
circuit between the relevant connector and
the battery is problem-free.
Continue to check the remainder of the
circuit in the same fashion.
When a point is reached at which no
voltage is present, the problem must lie
between that point and the previous test point
with voltage. Most problems can be traced to
a broken, corroded or loose connection.
Finding a short-circuit
To check for a short-circuit, first disconnect
the load(s) from the circuit (loads are the
components that draw current from a circuit,
such as bulbs, motors, heating elements, etc.).
Remove the relevant fuse from the circuit,
and connect a circuit tester or voltmeter to the
fuse connections.
Switch on the circuit, remembering that
some circuits are live only when the ignition
switch is moved to a particular position.
If voltage is present (indicated either by the
tester bulb lighting or a voltmeter reading, as
applicable), this means that there is a short-
circuit.
If no voltage is present, but the fuse still
blows with the load(s) connected, this indicates
an internal fault in the load(s).
Finding an earth fault
The battery negative terminal is connected
to “earth” (the metal of the
engine/transmission and the car body), and
most systems are wired so that they only
receive a positive feed. The current returning
through the metal of the car body. This means
that the component mounting and the body
form part of that circuit. Loose or corroded
mountings can therefore cause a range of
electrical faults, ranging from total failure of a
circuit, to a puzzling partial fault. In particular,
lights may shine dimly (especially when
another circuit sharing the same earth point is
in operation). Motors (e.g. wiper motors or the
radiator cooling fan motor) may run slowly,
and the operation of one circuit may have an
affect on another. Note that on many vehicles,
earth straps are used between certain
components, such as the engine/transmission
and the body, usually where there is no metal-
12•2Body electrical systems
Warning: Before carrying out
any work on the electrical
system, read through the
precautions given in “Safety
first!” at the beginning of this manual, and
in Chapter 5.
Caution:If the radio/cassette player fitted
to the vehicle is one with an anti-theft
security code, as the standard unit is, refer
to “Radio/cassette player anti-theft system
- precaution”in the Reference Section of
this manual before disconnecting the
battery.