1988 PONTIAC FIERO Service Repair Manual

TROUBLESHOOTING TESTS
TESTING FOR VOLTAGE DROP
This test checks for voltage being lost along
a wire, or through a connection or switch.
1. Connect the positive lead of a voltmeter to
the end of the wire (or to one side of the con-
nection or switch) which
is closer to the Bat-
tery.
2. Connect the negative lead to the other end
of the wire (or the other side of the connec-
tion or switch).
3. Operate the circuit.
4. The voltmeter will show the difference in
voltage between the two points.
A dif-
ference (or drop) of more than one volt indi-
cates a problem.
Voltage Drop Test
TESTING FOR SHORT TO GROUND
With
a Test Light or Voltmeter
1. Remove the blown fuse and disconnect the
load.
2. Connect a test light or voltmeter across the
fuse terminals (be sure that the fuse is
powered).
3. Beginning near the fuse block, wiggle the
harness from side to side. Continue this at
convenient points (about
6 inches apart)
while watching the test light or voltmeter.
4. When the test light glows, or the \voltmeter
registers. there is a short to ground in the
wiring near that point.
Testing For Short With Test Light
or Voltmeter
With a Self-Powered Test Light or Ohmmeter
1. Remove the blown fuse and disconnect the
battery and load.
2. Connect one lead of a self-powered test light
or ohmmeter to the fuse terminal on the
load side.
3. Connect the other lead to a known good
ground.
4. Beginning near the fuse block, wiggle the
harness from side to side. Continue
this at
convenient points (about
6 inches apart)
while watching the self-powered test light or
ohmmeter.
,5. M'hen the self-powered test light glows, or
the ohmmeter registers. there is a short to
ground in the wiring near that point.
SELF POWERED
DISCONNECTED
Testing For Short With Self-Powered
Test Light or Ohmmeter

TROUBLESHOOTING TESTS m r rn 0
With a Short Finder
1. Remove the blown fuse, leaving the Battery
connected.
2. Connect the Short Finder across the fuse
terminals.
3. Close all switches in series with the circuit
you are troubleshooting.
4. Operate the Short Finder. The Short Finder
will pulse current to the short. This creates
a pulsing magnetic field surrounding the
circuit wiring between the fuse block and
the short.
5. Beginning at the fuse block. slowly move
the Short Finder meter along the circuit
wiring. The meter will show current pulses
through sheet
inetal and body trim. As long
as the meter is between the fuse block and
the short, the needle will move with each
current pulse. When you have
moved the
meter past the point of the short. the needle
will stop
moving. Examine the wiring in
that area for the short to ground.
Fuses Powering Several Loads
1. Find the schematic in Fuse Block Details
(8A-11) for the fuse that has blown.
2. Open the first connector or switch leading
from the fuse to each load.
3. Replace the fuse.
@ If the fuse blows, the short is in the
wiring leading to the first connector or
switch. Use a test light, meter, or short
finder as described above.
@ If fuse does not blow, go to next step.
4. Close each connector or switch until the PROPER JUMP STARTING PROCEDURES
fuse blows, to find which circuit the short is
With the use of electronic components (such
in. Connect test lamp, meter, or short finder
as solid-state radios, electronic control
mod- at the connector to the suspect circuit (dis- ules, and others) becoming more wide-spread
connected) rather than at the fuse termi- each model year, the potential for damage nals. caused by improper jump starts increases. The
SHORT FUSE FINDER - BLOCK -
MOVE METER
NEEDLE STOPS
MOVING HERE
NO PULSING
MAGNETIC
FIELD
Cb
SHORT TO
GROUND
w-
Finding Short With Short Finder
following guidelines are presented to reduce
the likelihood of such damage.
JUMP START ONLY IF BUILT-IN
HYDROMETER "EYE" ON BATTERY IS
DARK. If the "eye" is clear or yellow, do not
attempt to jump start. If the "eye" is green,
the Battery is charged and does not require a
jump start. Both the booster and the dis-
charged Battery should be treated carefully
when using jumper cables.
CAUTION: Do not expose the Battery to
open flame or sparks. Serious personal
injury, particularly
to the eyes, may result
from
a Battery explosion, Battery acid, or
electrical burns.
The Ignition Switch must be in OFF
when connecting or disconnecting the
jumper cables.
All accessories. including the Radio.
should be turned off before jump start-
ing.
Cable polarity must be correct. Compo-
nent damage can occur
if the polarity is
re~~ersed. even if only briefly.
a Connect the positive jumper cable first.
then connect the negative cable to the
engine ground (not the negative termi-
nal of the dead Battery).

REPAIR PROCEDURES 0) B
ELECTRICAL REPAIRS
This section provides instruction in the fol-
lowing repairs:
- Circuit Protection
- Typical Electrical Repairs
- Splicing Copper Wire
- Splicing Aluminum \l.ire
- Splicing Txisted Shielded Cable
- Repairing Connectors (Except Weather
Pack
V and
- Repairing breather I'ack * (Environmen-
tal) Connectors
Note: After any electrical repair is made, always
test the circuit by operating the devices in the
circuit. This confirms not only that the repair is
correct, but also that the cause of the complaint
was correctly identified.
CIRCUIT PROTECTION
All electrical circuits are protected against
excessive loads which might occur because of
shorts or overloads in the wiring system. Such
protection is
prolrided by a fuse. circuit
breaker. or fusible link.
Fuses
The most common method of automotive
wiring circuit protection is the fuse. Whenever
there is an excessive amount of current flow-
ing through a circuit the fusible element will
melt and create an open or incomplete circuit (see
Figure
1). Fuses are a "one time" protec-
tion device and must be replaced each time the
circuit is overloaded.
Auto-fuses are color coded. The standard-
ized color identification and ratings are shown
in Figure
2.
For senrice replacement. non-color coded
fuses of the same respective current rating can
be used. The current rating of each fuse is
molded into its head.
To determine whether or not an auto-fuse is
blown, remove the suspect fuse and examine
the element in the fuse for a break, (see Figure
1). If the element is broken, replace the fuse
with one of equal current rating.
There are, however. additional specific cir-
cuits with in-line fuses. In-line fuses are
located within the individual wiring harness.
They are usually housed in spring-loaded,
twist-type receptacles.
GOOD FUSE BLOWN FUSE
Figure 1 - Sample Fuses Figure
2 - Fuse Rating And Galor
CURRENT
RATING
(AMPERES)
3
5
7.5
10
15
20
2
5
30
Circuit Breakers
COLOR
VIOLET
TA N
BROWN RED
BLUE
YELLOW
WHITE
GREEN
A circuit breaker is a protective device
designed to open the circuit when a current
load is in excess of rated breaker capacity. If
there is a short or other type of overload condi-
tion in the circuit, the excessive current will
open the circuit between the circuit breaker
terminals. The circuit breaker will remain open
until the trouble is found and corrected. The
circuit breaker will close automatically when
the excessive current is removed. The condi-
tion of a circuit breaker may be verified by
removing it from the circuit and checking the
resistance.
A good circuit breaker will have
less than
1 ohm resistance between the two ter-
minals.

REPAIR PROCEDURES
Fusible Links
In addition to circuit breakers and fuses,
some circuits use fusible links to protect the
wiring. Like fuses, fusible links are "one time
"
protection devices that will melt and create an
open circuit (see Figure
3).
Not all fusible link open circuits can be
detected by observation. Always inspect that
there is Battery voltage past the fusible link to
verify continuity.
Fusible links are used instead of a fuse in
wiring circuits that are not normally fused,
such as the ignition circuit. Each fusible link is
four wire-gauge sizes smaller than the cable it
is designed to protect. Links are marked on the
insulation with wire-gauge size because the
heavy insulation makes the link appear to be a
heavier gauge than it actually is. The same
wire size fusible link must be used when replac-
ing a blown fusible link.
FUSIBLE LINK BEFORE SHORT CIRCUIT
, BROKEN CIRCUIT INSIDE INSULATION
Fusible links are available with two types of
insulation: Hypalon
bnd SiliconelGXL (SILI
GXL). Service fusible links made with SILI
GXL may be used to replace either Hypalon "
or SILIGXL fusible links. Service fusible links
made with
Hypalonday only be used to
replace Hypalon
"fusible links. To determine
the fusible link type: nick the insulation of the
blown fusible link with a knife.
SILIGXL will
have a white inner core under the outer color.
Hypalon
"nsulation is one color. Service fusi-
ble links are available in many lengths. Choose
the shortest length that is suitable.
If the fusi-
ble link is to be cut from a spool, NEVER make
a fusible link longer than 228 mm
(9 in).
CAUTION: Fusible links cut longer than
228 mm
(9 in) will not provide sufficient
overload protection.
To replace a damaged fusible link, cut it off
beyond the splice. Replace with a repair link.
When connecting the repair link. strip wire
and use staking-type pliers to crimp the splice
securely in two places (see Figure
4). For more
details on splicing procedures see Splicing
Copper Wire.
R SHORT CIRCUIT
Figure 3 - Good And Damaged Fusible Links
-- - - - - -- - - - - -- - - -

To replace a damaged fusible link which TVPlCAL ELECTRlCAL REPAIRS
feeds two harness wires. cut then1 both off
An open circuit is an incomplete circuit.
be?-ond the splice. Use two repair links. one I'ower cannot reach the load or reach ground.
spliced to each harness wire (see Figure -5). If a circuit is open. active components do not
energize.
A short circuit is an unwanted con-
nection between one part of the circuit and
either ground or another part of the circuit. A
short circuit causes
a fuse to blow or a circuit
breaker to open. Short
Circuits Caused
by
Darnaged Wire Insulation
--Locate the damaged wire.
-Find and correct the cause of the wire
insulation damage.
-For minor damage, tape over the wire.
If
damage is more extensive, replace the
faulty segment of the wire. (Refer to the
splicing instructions for copper, alumi-
num, or shielded cable for the correct
splicing procedure.)
REPAIR PROCEDURES
SPLICING COPPER WIRE
Q) D
Step One: Open the Harness
If the harness is taped, remove the tape. To
avoid wire insulation damage, use a sewing
"seam ripper" to cut open the harness (avail-
able from sewing supply stores).
If the harness has a black plastic conduit,
simply pull out the desired wire. Note that alu-
minum wire is enclosed in brown conduit.
Refer to Splicing Aluminum Wire if necessary.
Step Two: Cut the Wire
Begin by cutting as little wire off the har-
ness as possible. You may need the extra
length of wire later if you decide to cut more
wire off to change the location of a splice. You
may have to adjust splice locations to make
certain that each splice is at least
40mm (1 112 ")
away from other splices, harness branches, or
connectors.
Figure 4 - Single Wire Feed Fusible Link
Figure 5 - Double Wire Feed Fusible Link

REPAIR PROCEDURES
Step Three: Strip the Insulation
When replacing a wire. use a wire of the same
size as the original wire or larger. The schemat-
ics list wire size in metric units. The following
table (see Figure
6) shows the commercial
(AWG) wire sizes that can be used to replace
each
metric wire size. Each AWG size is either
equal to or larger than the equivalent metric
size.
METRIC WIRE
SIZES
.22
.35
.5
.8
13.0
32.0
AWG
SIZES
Figure 6 - Wire Size Conversion Table
To find the correct wire size either find the
wire on the schematic page and convert the
metric size to the AR'G size. or use an
An'(;
wire gage.
If you aren't sure of the wire size. start with
the largest opening in your wire stripper and
work down until you get a clean strip of the
insulation. Be careful to avoid nicking or cut-
ting any of the wires.
Check the stripped wire for nicks or cut
strands. If the wire is damaged. repeat the pro-
cedure on a new section of wire. The two
stripped wire ends should be equal in length.
Step Four: Crirnp the Wires
Select the proper clip to secure the splice. '1'0
determine the proper clip size for the wire
heing spliced. follow the directions included
with your clips. Select the correct anvil on the
crimper. (On most crimpers your choice is
lim-
ited to either a small or large anvil.) Overlap
the two stripped wire ends and hold them
between your
thumb and forefinger as shown
in Figure
7. Then, center the splice clip under
the stripped wires and hold it in place.
-Open the crimping tool to its full width
and rest one handle on a firm flat surface.
--Center the back of the splice clip on the
proper
anvil and close the crinlping tool
to the point where the former touches the
wings of the clip. -Make
sure that the clip and wires are still
in the correct position. Then, apply
steady pressure until the crimping tool
closes (see Figure
8).
Before crimping the ends of the clip, be sure
that:
--The wires extend beyond the clip in
each direction.
-No strands of wire are cut loose, and
-No insulation is caught under the clip.
Crirnp the splice again. once on each end. Do
not let the crimping tool extend beyond the
edge of the clip or you may damage or nick the
wires (see Figure
9).
/ CENTERED ON ANVIL
Figure 8 - Crimping The Splice Clip

REPAIR PROCEDURES
ALIGN TOOL WITH EDGE OF CLIP
Step Five: Solder
Apply 60140 rosin core solder to
t,he opening
in the back of the clip (see Figure
10). Follow
the manufacturer's instructions for the solder
equipment you are using.
Step Six: Tape the Splice
Center and roll the splicing tape. The tape
should cover the entire splice. Roll on enough
tape to duplicate the thickness of the insula-
tion on the existing wires. Do not flag the tape.
Flagged tape may not provide enough insula-
tion, and the flagged ends will tangle with the
ot,her wires in the harness (see Figure 11).
If the wire does not belong in a conduit or
other harness covering, tape the wire again.
Use a winding motion to cover the first piece of
tape (see Figure 12).
Figure 9 - Completing The Grirnp
SPLICING ALUMINUM WIRE
General Motors cars have a front body wir-
ing harness made of 2.0 metric and 1.0 metric
(14 and 16 gauge) insulated solid cable alumi-
num wires. These wires are enclosed in a brown
solid plastic conduit from behind the instru-
ment panel to the rear of the car..
A special repair kit (1684873-GR.2.530-KIT-
ALUM-WIRE
TERMINAL REPAIR) is
available to help make repairs on aluminum
wires. This kit contains materials and instruc-
tions that can be used either to splice wire or
crimp on new terminals. The kit includes the
following parts:
Figure 10 - Applying The Solder
GOOD (ROLLED)
BAD (FLAGGED)
Figure
11 - Proper First Taping

REPAIR PROCEDURES
TAPE AGAIN IF NEEDED
Figure
12 - Proper Second Taping
-Small cylindrical metal splice clips.
-A plastic tube of petroleum jelly.
-Ten 2.0 metric
(14 gauge) DK GRN leads:
lv50mm (6 "1 long with terminals.
-Ten 1.0 metric
( 16 gauge) BRN leads: 150
mm
(6") long with terminals.
Use of the special materials in this kit will
help prevent galvanic corrosion. Galvanic
ror-
rosion causes increased resistance between the
terminal and wire. or the splice clip and wire. or
both. Increased resistance would affect the
operation of the electrical components in the
repaired circuit.
Step One: Open the Harness
Because the harness has a solid plastic con-
duit. simply cut the conduit open with
diagonal cutters and pull out the desired wire.
Be careful not to damage any of the wires when
cutting open the conduit.
Step Two: Cut the Wire
Begin by cutting as little wire off the har-
ness as possible. You may need the extra
length of wire later if you decide to cut more
wire off to change the location of a splice. You
ma?. have to adjust splice locations to make
certain that each splice is at least 40mm
(1 112")
away from the other splices. harness branches.
or connectors.
Step Three: Strip the Insulation
When replacing a wire or lead. use a wire of
the same size as the original wire, or larger.
Look up the metric wire size on the schematic
and select the proper-sized leads from the spe-
cial repair kit. Remember that the wires in this
harness can only be one of two sizes-2.0 metric
or 1.0 metric
(14 or 16 gauge).
Use wire strippers of the proper gauge to
strip approximately 6mm (114
") of insulation
from each wire end.
When stripping the outer jacket from the
aluminum wire core. be careful not to nick or
damage the core.
A damaged core will weaken
the assembly at this point.
Step Four: Coating the SpliceITerminal
To prevent corrosion, apply a generous coat-
ing of petroleum jelly to the splice area.
If you
are replacing a lead, also thoroughly coat the
terminal crimp area and aluminum core with
petroleum jelly. Both areas are shown in Fig-
ure
13 and identified with the letter "A."
Step Five: Crimp the Wires
-Select the proper-sized splice clip (follow
the instructions included in the special
repair kit).
-Place one wire end in each end of the
splice clip.
-Crimp the clip firmly to the wire using
10" slip joint pliers. Do NOT solder the
splice (see Figure 14).
-Repeat this procedure for the second wire
or lead in the splice clip.
Figure 13 - Where To Apply Petroleum Jelly