1993 FORD SIERRA sensor

System type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12 volt, negative earth
BulbsFittingsWattage
Halogen headlamps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .H460/55
Auxiliary driving lamps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .H355
Front foglamps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .H355
Side lamps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Glass base5
Direction indicator lamps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Bayonet21
Brake/tail lamps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Bayonet21/4
Reversing lamp(s) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Bayonet21
Rear foglamp(s) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Bayonet21
Rear number plate lamps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Glass base5
Luggage compartment lamp . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Bayonet10
Underbonnet lamp . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Bayonet10
Courtesy lamp(s) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Bayonet10
Map reading lamps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Glass base5
Vanity mirror illumination lamp . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Festoon3
Glove compartment lamp . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Glass base3
Ashtray lamp . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Glass base1.2
Warning lamps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Glass base1.2 or 2.5
Instrument illumination lamps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Glass base1.2 or 2.5
Heater control illumination lamp . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Glass base1
Automatic transmission gear selector lamp . . . . . . . . . . . . . . . . . . . . . .Bayonet1.2
Clock illumination lamp . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Bayonet1.4
Cigarette lighter lamp . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Glass base1.2
Torque wrench settingsNmlbf ft
Trip computer fuel flow sensor unit fuel pipe unions . . . . . . . . . . . . . . .14 to 1710 to 13
General information
The electrical system is of the 12 volt.
negative earth type. Electricity is generated by
an alternator, belt-driven from the crankshaft
pulley. A lead-acid storage battery provides a
reserve of power for starting and when the
demands of the system temporarily exceed
the alternator output.
The battery negative terminal is connected
to “earth” - vehicle metal - and most electrical
system components are wired so that they
only receive a positive feed, the current
returning via vehicle metal. This means that
the component mounting forms part of the
circuit. Loose or corroded mountings can
therefore cause apparent electrical faults.
Many semiconductor devices are used in
the electrical system, both in the “black
boxes” which control vehicle functions and in
other components. Semiconductors are very
sensitive to excessive (or wrong polarity)
voltage, and to extremes of heat. Observe the
appropriate precautions to avoid damage.
Precautions
It is necessary to take extra care when
working on the electrical system to avoid
damage to semi-conductor devices (diodes
and transistors), and to avoid the risk of
personal injury. In addition to the precautions
given in the
“Safety first!” Section at the
beginning of this manual, take note of the
following points when working on the system.
Always remove rings, watches, etc before
working on the electrical system. Even withthe battery disconnected, capacitive
discharge could occur if a component live
terminal is earthed through a metal object.
This could cause a shock or nasty burn.
Do not reverse the battery connections.
Components such as the alternator or any
other having semi-conductor circuitry could
be irreparably damaged.
If the engine is being started using jump
leads and a slave battery, connect the
batteries positive to positive and negative to
negative. This also applies when connecting a
battery charger.
Never disconnect the battery terminals, or
alternator multi-plug connector, when the
engine is running.
The battery leads and alternator multi-plug
must be disconnected before carrying out any
electric welding on the car.
Never use an ohmmeter of the type
incorporating a hand cranked generator for
circuit or continuity testing.
Note:Refer to the precautions given in “Safety
first!” and in 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 unit (ECU) is involved.General
1A 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 andconnectors which link the component to both
the battery and the chassis. To help to pinpoint a
problem in an electrical circuit, wiring diagrams
are included at the end of this Chapter.
2Before attempting to diagnose an electrical
fault, first study the appropriate wiring
diagram, to obtain a more 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.
3Electrical 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. 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,
in order to pinpoint the trouble-spot.
4The basic tools required for electrical fault-
finding include: a circuit tester or voltmeter (a
12-volt bulb with a set of test leads can also
be used for certain tests), a self-powered test
light (sometimes known as a continuity tester),
an ohmmeter (to measure resistance), a
battery and set of test leads, and 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.
2Electrical fault-finding - general
information
1General information and
precautions
13•2Body electrical system
Specifications

Speedometer
12Remove the panel lens (paras. 5 and 6).
13Remove the two screws securing the
speedometer to the rear of the instrument
panel, taking care not to lose the two brushes.
Withdraw the speedometer through the front
of the instrument panel.
14Refitting is a reversal of removal.
Tachometer
Models up to 1990
15Remove the four or five securing screws,
as applicable, and separate the two halves of
the instrument panel housing.
16Remove the three securing nuts and
washers from the rear of the instrument panel
housing, and withdraw the tachometer.
17Refitting is a reversal of removal, but ensure
that the tachometer engages with the locating
ribs in the housing around the dial edge.
Models from 1990
18The procedure is as described above but
before the tachometer can be withdrawn from
the instrument panel housing, the printed circuit
board must be carefully pulled from the
tachometer terminals. Ensure that the printed
circuit board is pushed fully home when refitting.
Fuel and temperature gauges
Models up to 1987
19Remove the four securing screws and
separate the two halves of the instrument
panel housing.
20Remove the four securing nuts and washers
from the rear of the instrument panel housing,
and withdraw the combined gauge assembly.
21Refitting is a reversal of removal.
Models from 1987
22Remove the five securing screws and
separate the two halves of the instrument
panel housing.
23Remove the printed circuit board as
described previously in this Section.
24On “low specification” models, remove the
two securing screws from the front of the
gauge assembly, then withdraw the combined
gauge assembly from the printed circuit board.25On “high specification” models, simply
withdraw the combined gauge assembly from
the printed circuit board.
26Refitting is a reversal of removal, but on
“high specification” models, ensure that the
gauge assembly engages with the locating
ribs in the housing around the gauge edge.
1Disconnect the battery negative lead
Computer module
2Remove the single screw from the top edge
of the facia panel in which the module is
housed, then withdraw the facia panel.
3Remove the four now exposed securing
screws, disconnect the wiring plug, and
carefully withdraw the module. On later
models a retaining lug must be depressed
before the wiring plug can be disconnected.
4Where applicable, the mounting brackets
can be removed from the module by
unscrewing the securing nuts.
5If necessary, the illumination bulb can be
removed from the module by twisting the
bulbholder anti-clockwise using a pair of long-
nosed pliers. The bulb is a push-fit in the holder.
6Refitting is a reversal of removal.
Speed sender unit
Models up to 1987
7The speed sender unit is located in the
engine compartment on the right-hand side of
the bulkhead.
8Disconnect the plug from the sender unit.
9Unscrew the two knurled nuts from the
sender unit and disconnect the two
speedometer cables.
10Remove the three securing screws and
remove the bracket and sender unit.
11Unscrew and remove the securing nut
and washer, and separate the sender unit
from the bracket.
12Refitting is a reversal of removal.
Models from 1987
13Detach the wiring, hose retainers andcover panel from the bulkhead to gain access
to the sender unit.
14Proceed as shown in paragraphs 7 to 9.
15Remove the retaining nut and washer and
withdraw the sender unit.
16Refitting is a reversal of removal.
Fuel flow sensor unit
Carburettor models
17The fuel flow sensor is located on the left-
hand side of the engine compartment (see
illustration).
18Disconnect the wiring plug from the
sensor unit.
19Refer to the “Safety first!” Section at the
front of the manual, and the precautions in
Chapter 4, then disconnect the fuel pipes from
the sensor unit. Note that on models up to
1987 there are three fuel pipe connections, and
on models from 1987 there are two fuel pipe
connections. Be prepared for fuel spillage.
20Remove the three securing screws and
withdraw the bracket and sender unit.
21Unscrew the four nuts and separate the
sender unit from the bracket.
22Refitting is a reversal of removal, but
ensure that the flow direction arrows on the
fuel inlet and outlet ports are correctly
orientated, and that the arrow on the rear of
the unit points to the top.
Fuel injection models
23The sensor is located on the left-hand
side of the engine compartment.
24Disconnect the wiring plug from the
sensor unit.
25Refer to the “Safety first!” Section at the
front of the manual, and the precautions in
Chapter 4, then unscrew the two union nuts
and disconnect the fuel pipes from the sensor
unit. Be prepared for fuel spillage.
26Remove the two securing screws and
withdraw the sensor unit.
27Refitting is a reversal of removal, but
ensure that the No 2 injector fuel pipe is fitted
to the sensor unit outlet port marked with an
arrow, and ensure that the union washers are
in place (see illustration). Tighten the fuel
pipe unions to the specified torque.
22Trip computer components -
removal and refitting
13•8Body electrical system
22.17 Trip computer fuel flow sensor unit location - carburettor
models up to 1987. Bracket retaining screws arrowed
22.27 Trip computer fuel flow sensor unit - fuel injection models
A Wiring plug
B Hollow bolts
C Inlet port banjo connectorD Bracket
E Outlet port banjo connector
F Sensor unit

Location
1The AWS control unit, and (when fitted) the
bulb failure monitor, are located behind the
glovebox on models up to 1987.
2On models from 1987, the control and bulb
failure modules are located behind the driver’s
side footwell trim panel.
Testing
3Thorough testing and fault finding should
be left to a Ford dealer or other electrical
specialist, having test equipment. Unskilled or
uninformed testing may cause damage.
4Investigation of malfunctions should begin
by checking that all wiring is intact and
securely connected. If checking wires or
sensors for continuity, always disconnect the
control unit and/or bulb failure monitor before
so doing, otherwise damage may be caused.
5Note that false oil level readings can result if
the car is parked on a slope. False bulb failure
warnings may occur if incorrect wattage bulbs
are fitted.
Removal and refitting
6Disconnect the battery negative lead.
Warning lamp bulbs
7Remove the single screw from the top edge
of the facia panel in which the warning lamps
are housed, then withdraw the facia panel
(see illustration).
8Twist the relevant bulbholder through 90º to
remove it from the rear of the facia panel. The
bulb is integral with the bulbholder and must
be renewed as a unit (see illustration).
9Refitting is a reversal of removal.
Graphic display unit and bulbs
10Remove the clock or trip computer.
11Remove the display unit retaining screw
and the retainer, then pull the unit forwards
and disconnect the wiring plug using a thin-
bladed screwdriver (see illustrations).
12To renew a bulb, remove the two securing
screws and pull the circuit board from the
back of the unit to reveal the bulbs. The bulbs
are a push-fit.
13Refitting is a reversal of removal.
Control unit and bulb failure monitor
14Unclip the trim panel from the lower edge
of the passenger side lower facia panel.
15On models up to 1987, pull off the two
clips to release the control unit/bulb failure
monitor mounting bracket. Depress the
retaining tab and disconnect the relevant
wiring plug, then remove the two securing
screws and withdraw the control unit/bulb
failure monitor (see illustration).
16On models from 1987, release the
retaining tang and carefully slide the control
unit/bulb failure monitor downwards. Depress
the retaining tab and disconnect the relevant
wiring plug, then withdraw the control
unit/bulb failure monitor.
17Refitting is a reversal of removal. Note
that when both a control unit and bulb failure
monitor are fitted, the control unit wiring plug
is coloured brown, and the bulb failure
monitor wiring plug is coloured green.
Ice warning sender
18This sender is located beneath the front
panel on the right-hand side of the vehicle.
19Where necessary, for improved access
remove the horn.
20Depress the two retaining tangs,
disconnect the wiring plug and withdraw the
sender unit from the slot in the front panel.
21Refitting is a reversal of removal.
Door/tailgate/boot lid ajar switches
22Remove the relevant lock.
23Pull the switch from its location in the lock
body, disconnect the wiring plug (if not
already done) and withdraw the switch (see
illustration).24Refitting is a reversal of removal.
Low coolant level sensor
25Refer to Chapter 3.
Low washer fluid level switch
26Syphon out the contents of the reservoir,
then prise the switch from its grommet using a
thin-bladed screwdriver. Disconnect the
wiring plug.
27Refitting is a reversal of removal, using a
new grommet if necessary. Use a little liquid
detergent as a lubricant.
28On completion, refill the reservoir.
Low fuel level switch
29The switch is integral with the fuel level
sender unit. Details of fuel level sender unit
removal and refitting are given in Chapter 4.
Low oil level switch
30The switch is integral with the oil level
dipstick. To remove, simply withdraw the
23Auxiliary warning system
components - location,
testing, removal and refitting
Body electrical system 13•9
13
23.11a Removing the graphic display unit
retaining screw
23.23 Door lock and door ajar switch23.15 Auxiliary warning system control unit
location
23.11b Disconnecting the wiring plug from
the graphic display unit
23.8 Removing an auxiliary warning lamp
bulb23.7 Remove the screw from the warning
lamp facia panel