PONTIAC FIERO 1988 Service Repair Manual

INSTRUMENT PANEL, GAGES & CONSOLE 8C-'I
SECTION 8C
NSTRUMENT PANEL, GAGES & CONSOLE
CONTENTS
General Description ................................... 8C-1
Instrument Panel and Gages ........................ 8C-1
Printed Circuit .......................................... 8C-1
Instruments ................................................... 8C- 1
Speed Sensors
............................ .. ............. 8C- 1
Pinion Gear
............................................. 8C-2
Photo Speed Sensor ................................ 8C-2
PM Generator ................... .. ...... ............... 8C-2
Speedometer ................................................ 8C-2
Mechanical ....................... .. .................... 8C-2
Quartz ........................ .. .......................... 8C-2
Digital .................... .. ...... ................. 8C-2
Fuel Gage .................................................... 8C-2
Temperature Warning Light ...................... 8C-3
Generator Warning Light ............................ 8C-3
Engine Oil Pressure Light ............................ 8C-3
"Service Engine Soon" Light ....................... 8C-3
Upshift Indicator Light .............................. 8C-3
Diagnosis .................... .. ........................... 8C-3
General Information .................................. 8C-3
Instrument Panel & Gages ...................... ..... 8C-3
On-Car Service ......................... .. ........... 8C-4
Instrument Panel Pad ................................... 8C-4
Instrument Panel Cluster ........................... 8C-4
Instrument Panel Carrier ............................. 8C-4
Headlight Switch .......................................... 8C-4
Console Mounted Switches and
Accessories
............................................... 8C-4
Console ......................................................... 8C-4
Speedometer .................................................. 8C-5
Illustra3ions ................................................. 8C-5
IP Pad ........................................................... 8C-5
IP Carrier ................................................... 8C-6
Instrument Cluster ....................................... 8C-6
Lower IP Covers ......................................... 8C-7
IP Trimplates ............................................... 8C-7
IP Hush Panels; with A/C .......................... 8C-8
..................... IP Lower Trim Pad (Console) 8C-8
Map Holder or Map Pocket ........................ 8C-8
IP Hush Panels; without A/C ..................... 8C-9
Radio Mounting ........................................... 8C-9
Subwoofer & Hatch Release
Switches/Covers ........................................ 8C- 10
Foglamp Switch/Cover ................................ 8C- 10
Oil Pressure and Temperature
Switches
..................................................... 8C-11
Heater/Ventilation/Defroster
Ductwork .................................................. 8C- 12
A/C and Defroster Ductwork ..................... 8C-13
Ram Vent System Ductwork ....................... 8C-14
Console Mounted Switches
&
Accessories ................................................. 8C- 14
Dash Insulators
............................................ 8C- 15
Heater Floor Outlet
..................................... 8C-15
................ Headlamp/Parking Lamp Switch 8C- 15
............. Dash Mounted Accessory Switches 8C- 15
GENERAL DESCRIPTION
INSTRUMENT PANEL AND GAGES
INSTRUMENTS
Instruments consist of fuel gage, temperature
The instrument panel on most cars is a sing,e unit indicator light, generator light, oil pressure indicator
design and all parts attach to the main instrument light, and speedometer. See Section 9F for optional
panel with clips and screws. To service the instrument Gages and tachometer. Service on instruments
panel and components see on-car service information, can be obtained through authorized repair stations.
However, knowledge of instrument circuit checks will
PRINTED CIRCUIT
All models are equipped with printed circuits
which supply current to most instrument panel lights
and instruments. These circuits are made of copper foil
which is die cut and bonded to a polyester base film
(usually mylar). The printed circuit electrical power is
supplied by a connector containing several wires, as
shown in the instrument panel wiring harness
installation instructions. The connector also helps
retain the printed circuit to the speedo cluster. The rest
of the circuit is retained by additional connectors (if
used) and snap-in
bulbs/sockets. For individual
printed circuit diagrams, see Section
8A-80/8 1/82/83,
'Instrument Panel'. help
in determining if operating difficulties lie in the
instrument itself or its related circuit.
Instruments have been designed for easy removal
by elimination of separate wiring. With the wiring
provisions integrated with the instrument panel wiring,
the instruments can be removed after removing the
trim and lens.
SPEED SENSORS
There are three speed sensors currently in use:
1. PINION GEAR; used in mechanical systems
2. PHOTO SPEED SENSORS; used in mechanical
systems
3. PM GENERATOR; used in electronic systems

842-2 INSTRUMENT PANEL. GAGES & CONSOLE
Pinion Gear
The PINION GEAR is attached to the
traaasmission/transaxle output shaft and rotates in
proportion to the speed of the car. This rotation is
transferred from the pinion gear to the speedometer
head by the speedometer cable.
Photo Speed Sensor
On vehicles that use a mechanical drag-cup
speedometer, the PHOTO SPEED SENSOR is
inserted into the frame of the mechanical speedometer
to provide an electrical feedback to the ECM that
represents vehicle speed. The ECM needs to know how
fast the car is traveling in order to control and operate
the cruise control, cooling fan, and transmission and
evaporative systems.
The photo speed sensor is made up of two special
electronic devices: a Eight-Emitting Diode (LED) and
a photo transistor (a light-sensitive amplifying device).
In the mechanical speedometer, there is a reflective
blade attached to the rotating magnet that is polished
to
reflect light from the LED back to the photo
transistor. Whenever the light strikes the photo
transistor, it conducts electricity. The rate that the
transistor conducts and does not conduct is
proportional to the speed of the magnet, which reflects
the speed of the vehicle. This voltage signal from the
photo transistor is sent to a buffer amplifier (part of the
speed sensor) to be conditioned to a signal the ECM
can understand and use.
PM Generator
The PM (Permanent Magnet) GENERATOR is
a small
AC generator used to sense vehicle speed. The
shaft of the generator fits into a pinion gear in the
transmission/transaxle output shaft (as does the cable
in
a mechanical system).
When the output shaft rotates, the magnet rotates
and generates a voltage. Except for the permanent
magnet, the
PM Generator is exactly like a miniature
alternator. The PM generator is constructed to provide
a voltage whose frequency is about
1.1 cycles per
second for every mile per hour of vehicle speed. This
signal is sent to a buffer amplifier, and then to the
speedometer and the
EGM.
SPEEDOMETER
The speedometer is a road speed indicator with
an odometer to record total mileage, and, on some cars,
a resettable trip odometer.
The major types of speedometers in use are
mechanical instruments and electronic instruments.
Mechanical speedometers use a dial needle to indicate
road speed. Electronic speedometers include
instruments that use a dial indicator and those using
bar-graph
LCD's (Liquid Crystal Displays) or VTF
(Vacuum Tube Fluorescent) displays.
Meehanice! Speedometers
A mechanical speedometer uses a cable driven
(through a pinion gear) by the transmission output
shaft. The cable connects to a magnetic drag-cup inside the
speedometer, which rotates the speedometer
needle. The end of the rotating cable causes a small bar
magnet to rotate within a metal cup. As the magnet
rotates within the cup, it magnetically attracts (drags)
the metal cup along behind it. Two things work to
prevent the cup from rotating as quickly as the magnet.
1. The distance of the magnet from the cup reduces
its effect on the cup.
2. A counterspring is wound around the shaft of the
cup in such a way as to oppose the normal
rotation of the cup. The counterspring loads the
drag-cup to give correct indication of the speed,
prevent needle overshoot, and also to return the
drag cup to a zero point.
Mechanical speedometers require a photo speed
sensor to provide road speed information for the ECM
and other systems, such as Cruise Control and the TCC
(Torque Converter Clutch).
The odometer on these instruments consists of
numbered wheels that are rotated by the speedometer
cable through worm gears.
Quartz Speedometer
The quartz speedometer is an electrically driven
instrument. The indicator needle is driven by a
precision DC motor, and is countersprung to provide
a mechanical load, prevent overshoot of the needle, and
return the indicator to zero when the road speed is
zero.
The source of speed information for a quartz
speedometer is the PM generator. From the PM
generator, speed information goes to the buffer
amplifier to be converted to digital voltage, and then
to the cluster circuitry, which interprets the speed of
the vehicle and produces small voltage to apply to the
speedometer motor.
The odometer on this instrument consists of
numbered wheels that are electrically driven by a
special precision DC motor called a stepper motor.
Digital Speedometer
Digital clusters utilize two types of displays: LCD
(Liquid Crystal Display) and VTF (Vacuum Tube
Fluorescent). They are used in digital speedometers
and bar-graph tachometers, fuel gages, etc.
Speed information entering the cluster from the
buffer amplifier is interpreted by a microcomputer
which controls the speed indication, the tachometer
display and the odometer reading.
The odometers associated with these instruments
utilize either numbered wheels driven by a small motor
or electronic displays. With an electronic display, the
mileage reading is stored in a computer chip (called a
non-volatile RAM chip; NVRAM) that does not
become 'erased' when the vehicle is turned off,
as the
display does not retain the information.
FUEL GAGE
An electrical fuel gage is used on all models,
consisting of an instrument panel gage and a fuel tank
pick-up. The fuel gage indicates the quantity of fuel in

INSTRUMENT PANEL. GAGES & CONSOLE 8C-3
tank only when ignition switch is turned to "ON" or
"ACCESSORY" positions.
When ignition is turned to "OFF" or "START"
positions, the pointer may come to rest at any position.
The letters
"E" and "F" on the fuel gage are used to
point out direction of indicator travel only.
TEMPERATURE WARNING LIGHT
The engine temperature warning light is
controlled by a thermal switch which senses engine
coolant temperatures.
When the ignition switch is turned to "START"
position, a test circuit is closed and the light will come
on to indicate whether the light is functioning properly.
It is important to note that with low boiling-point
coolants (such as plain water) the temperature light
may not come on even though the coolant is boiling.
GENERATOR WARNING LIGHT
The generator warning light, located in the
instrument cluster, should come on when the ignition
switch is turned
"ON" and engine is not running. If
not, either the bulb is burned out or wiring to generator
has an open circuit.
When the generator voltage output becomes
greater than the battery voltage, the
"GEN" light
should go out. This does not, however, indicate
whether the battery is being charged or if the voltage
regulator is functioning properly.
Checks of the charging system are covered in
Section 6D, 'Engine Electrical'.
ENGINE OIL PRESSURE LIGHT
The engine oil pressure warning light is mounted
in the instrument cluster and controlled by a pressure
operated switch located on the engine block. When the ignition switch is
in the
"run" or "start9' position, the
oil pressure light should come on. If not, the bulb is
burned out, there is an open circuit between the bulb
and the oil pressure switch, or there is an open circuit
between the oil pressure switch and the choke heater.
After the engine is running, the oil pressure light
should go out when the oil pressure reaches the correct
specification. If not an oil pressure problem, a faulty oil
pressure switch or an open circuit from the choke
heater fuse to the oil pressure switch is indicated.
"SERVICE ENGINE SOON" LIGHT
All cars have a "SERVICE ENGINE SOON"
light mounted in the instrument cluster. The
"SERVICE ENGINE SOON9' light should come on
during engine starting. The light may stay on
a short
time after the engine starts.
If the light comes on while
driving, service to the emission control system may be
required. See Section
6E and Section 8A-80,
'Instrument Cluster', for complete diagnosis and
wiring diagrams of the
""P;RVICE ENGINE SOON"
light circuit.
UPSHIFT INDICATOR LIGHT
If your vehicle has a manual transmission, there
may be an
''Upshift" light on the instrument panel.
This light is illuminated to indicate optimum shift
points throughout the range from optimum fuel
economy to optimum performance. When this light is
on, shift your transmission to the next higher gear
range if conditions permit. For fuel economy,
accelerate slowly and shift when the light goes on. For
performance, accelerate as desired and shift when the
light goes on.
Safe operation of the vehicle may require shifting
differently than indicated by the "Upshift" light to
adapt to weather, road or traffic conditions.
Downshifting one or more gears may be required
to keep the engine running smoothly or to maintain
satisfactory performance.
DIAGNOSIS
Diagnostic information for all instrument panel
electrical systems is found in Section
8A-80,
'Instrument Panel'.
CAUTION: When removing or
installing any electrical units,
disconnect the negative battery cable
to prevent possible short circuits
which could lead to personal injury
and/or property damage. When
replacing a speedometer or
odometer assembly, the law requires the
odometer reading of the replacement unit to
be set to register the same mileage as the
prior odometer.
if the same mileage cannot be
set, the
law requires that the replacement
odometer be set to zero and a label be
installed on the driver's door frame to show
the previous odometer reading and the date
of replacement.
GENERAL BNFORMATlOM
INSTRUMENT PANEL AND GAGES
The instrument panel is a single unit design and
and screws. To service the instrument panel and
all parts attach to the main instrument panel with clips components see Figs. 601 through 610.

8C.4 INSTRUMENT PANEL, GAGES & CONSOLE
ON-CAR SERVlCE
lNSTRUMEMT PANEL PAD
Figure 601
Remove or Disconnect
1. Four (4) screws in defroster ducts.
2. Screws
under lip of
I.P, pad.
3. I.P. pad from carrier.
lnstall or Connect
1. I.P. to carrier.
2. Screws
under lip of I.P. pad.
3. Four (4) screws in defroster ducts.
INSTRUMENT PANEL CLUSTER
Figure 683
Remove or Disconnect
1. Right and left lower trim plates. Removal of
lower I.P. covers not required.
2. Instrument cluster trim plate.
3. Six (6) cluster attachment screws, pull cluster
back and disconnect speedo cable and electrical
connections.
4. Trip odometer, reset knob (if so equipped) and
remove cluster lens.
5. Individual gages and/or speedo head are now
accessible for service or replacement. If service is
intended for only gages or tachometer, skip Step
3.
Install or Connect
1. Trip odometer, reset knob (if so equipped) and
remove cluster lens.
2. Six
(6) cluster attachment screws, pull cluster
back and disconnect speedo cable and electrical
connections.
3. Instrument cluster trim plate.
4. Right and left lower trim plates. Removal of
lower I.P. covers not required.
INSTRUMENT PANEL CARRIER
Figure 602
Remove or Disconnect
Negative battery cable.
Console. Instrument panel pad and lower hush panels.
Right and left lower I.P. covers and trim plates.
Instrument panel cluster and headlight switch.
Lower steering column.
Five (5) upper and six (6) lower I.P. carrier to
cowl screws.
Instrument panel electrical harness at cowl
(bulkhead) connector, and under dash.
I.P. carrier from car.
10. I.P. mounted components (A/C, defroster ducts,
wiring harness, etc.) are now accessible for service
or replacement.
11. Any seals or sealant damaged during
disassembly.
Install or Connect
I.P. carrier to car.
Instrument panel electrical harness at cowl
(bulkhead) connector, and under dash.
Five (5) upper and six (6) lower I.P. carrier to
cowl screws.
Steering column.
Instrument panel cluster and headlight switch.
Right and left lower I.P. covers and trim plates.
Instrument panel pad and lower hush panels.
Console.
Negative battery cable.
HEADLIGHT SWITCH
Figure 620
Remove or Disconnect
1. Right and left lower trim plates. Removal of
lower I.P.
cover(s) not required.
2. I.P. cluster trim plate.
3. Two (2) switch assembly retaining screws.
4. Depress side tangs and pull switch assembly from
I.P.
5. Individual switches of assembly are now
accessible for service or replacement.
Install or Connect
1. Depress side tangs and replace switch assembly
to I.P.
2. Two
(2) switch assembly retaining screws.
3. I.P. cluster trim plate.
4. Right and
left lower trim plates. Removal of
lower I.P.
cover(s) not required.
DASH MOUNTED ACCESSORY SWITCHES
Figure 62 1
Installation for various dash mounted accessory
switches is shown in Fig.
62 1.
CONSOLE MOUNTED SWITCHES AND
ACCESSORIES
Figure 6 17
Installation of various console mounted switches,
lights and accessories is shown in Figure 617.
CONSOLE
Remove or Disconnect
1. Negative battery cable.
2. Shift gate trim plate. Requires removal
of shift
handle and seven (7) screws.
3. Radio/A/C-heater controller trim plate.

INSTRUMENT PANEL, GAGES & CONSOLE 8C-5
4. A/C-heater controller (see Section 1B).
5. Radio (see Section 9A).
6. Electrical connectors (cigar lighter, ash tray light,
etc.) and pull harness forward out of console.
7. Six (6) console hold-down and two (2) console to
I.P. screws and remove console.
Install or Connect
1. Six (6) console hold-down and two (2) console to
I.P. screws and replace console.
2. Electrical connectors (cigar lighter, ash tray light,
etc.) and pull harness forward out of console.
3. Radio (see Section 9A).
4. A/C-heater controller (see Section 1B).
5. Radio/A/C-heater controller trim plate.
6. Shift gate trim plate.
7. Negative battery cable.
SPEEDOMETER
Figures 603
Remove or Disconnect
Right and left lower trim plates. Removal of
lower
I.P. cover(s) not required.
Instrument cluster trim plate.
Six (6) cluster attachment screws, pull cluster
back and disconnect speedo cable.
Cluster lens.
Two (2) screws retaining speedo head in cluster
from rear.
Electrical (VSS) connectors and remove speedo
head.
Install or Connect
Electrical (VSS) connectors and replace speedo
head.
Two (2) screws retaining speedo head in cluster
from rear.
Cluster lens.
Six (6) cluster attachment screws, reconnect
speedo cable, replace cluster.
Instrument cluster trim plate.
Right and left lower trim plates.

1 -SUPPORT
2-NUT
3-BOLTISCREW
4-PANE
L ASM.
Fig. 602 IP Carrler
Fig. 603 Instrument Cluster

INSTRUMENT PANEL, GAGES & CONSOLE 86-7
1 - RH COVER 5 - WIO A/C
2- RETAINER 6- IP LOWER
REINFORCEMENT
3 - PLATE
7 - BRACKET
4- STEERING
COLUMN FILLER
8- CONVENIENCE
PANEL CENTER
MOUNTING
BRACKET
H20043-8C
Fig. 604 Lower IP Covers

Fig. 606 I? Hush Panels; with A/C
1 -PAD ASM. 4- BRACKET
1 2-4 N*m (36 LB. IN.) 5-TRIM PLATE
1 3-6 Nem (54 LB. IN.)
Fig. 607 IP Lower Trim Pad (Console)
1 - MAP HOLDER 2- MAP POCKET
Fig. 608 Map Holder or Map Pocket

INSTRUMENT PANEL, GAGES & CONSOLE 8C-9
2-INSTRUMENT PANEL 7-NUT
3-LH VENT DUCT EXTENSION
8 -ACCE L. PEDAL BR K'T.
4-LH INSULATOR ASM.
9-REST ON EXISTING DASH STUD
5-BOLT/SCREW 10-RH INSULATOR ASM.
Fig. 609
IP Hush Panels; w/o A/C
1 --RADIO ASM.
3-BRACKET 5- BOLTISCREW (3) 7 - BUMPER 2- BRACKET 4-BOLTISCREW (4) 6-NUT 8- I/P LOWER TRIM PAD
Fig. 610 Radio Mounting