1988 PONTIAC FIERO Service Repair Manual

HEATER

HEATER
TROUBLESMOOTlNG HINTS
e Try the following checlcs before doing the
System Check.
1. If the Blower Motor does not operate at all,
check the
HTR A/C Fuse.
2. If the Blower Motor does not operate at all,
check that
GI08 is clean and tight.
3. If the Blower Motor does not turn off, in-
stall
a new Blower Switch.
r Go to System Check for a guide to normal
operation.
r Go to System Diagnosis for diagnostic tests.
SYSTEM CHECK
Use the System Check Table as a guide to
normal operation.
e Refer to System Diagnosis for a list of symp-
toms and diagnostic steps.
SYSTEM CHECK TABLE
ACTION 1 NORMALRESUU 1
COMPONENT LOCATION Page-Figure
Blower Motor (Without
AlC) ....... RH front of dash, behind strut tower .......... 201-14-D
Blower Resistors (Without AIC) .... RH front side of heater housing .............. 201-14-D
Fuse Block.
..................... Behind LH side of IIP, below light switch. ...... 201-10-8
C202 (1 cavity) .................. Behind center of UP, near control head. ........ 201-14-C
GPO8 .......................... RH front of dash, above center of Blower Motor . 201-14-D
SYSTEM DIAGNOSIS
Do the tests listed for your symptom in the
Symptom Table below.
Tests follow the Symptom Table.
SYMPTOM TABLE
A: BLOWER SWITCH TEST
0 If your symptom does not appear in the (A: BLOmR SWITCH TEST continued on Sympton Table perForm all of the Tests. next page)
not normal. Measure:
VOLTAGE
At: BLOWER
SWITCH CONNECTOR
(Connected)
Condition:
a ignition Switch: RUN
Measure Correct For
Between Voltage Diagnosis
P P
See 1
Blower Switch: LO
&
Ground Battery
See 2
* Blower
Switch: MED
(LT BLU)
& Ground
* Blower Switch: HI
Battery
See 2

HEATER
(A: BLOWER SWITCH TEST continued from
previous page)
1. Check/repair BRN (50) wire for an open
(see schematic).
3: BLOWER RESlSTORS TEST
Measure: VOLTAGE
At: BLOWER RESISTORS CONNECTOR
(Disconnected)
Conditions:
* lgnition Switch: RUN
Blower Switch: LO
Measure Correct
For
Between Voltage
Diagnosis
[ 0 Blower Switch: MED
A(LTBLU' I Battery I See 2 & Ground I
2 BLOWER MOTOR TEST
R CONNECTOR
(Disconnected)
Conditions:
* lgnition Switch: RUN
ORN wire & Battery Ground See 1
ORN wire & I Battery I See 2 BLK wire I
0 If
all results are correct, replace the
Blower Motor.
1. Perform Blower Switch Test. If Blower
Switch is OK,
check/repair ORN (52)
wire for an open (see schematic).
2. Check BLK (150) wire for an open (see
schematic).
CIRCUIT OPERATION
The Blower Motor delivers air to the inte-
rior of the vehicle. Its speed is controlled by
the Blower Switch and the Blower Resistors.
When the Ignition Switch is in RUN, battery
voltage is applied to the Blower Switch. With
the Blower Switch in LO, voltage is applied
across both Blower Resistors and the Blower
Motor. The Blower Motor runs at its slowest
speed. With the Blower Switch in MED, one of
the Blower Resistors is bypassed and the
Blower Motor runs faster. When the Blower
Switch is set to
HI, battery voltage is applied
directly to the Blower Motor and the Blower
Motor runs at its fastest speed.
0 If all results are correct, replace the
Blower Resistors.
1. Check/repair YEL (51) wire for an open
(see schematic).
2. Check/repair LT BLU (72) wire for an
open (see schematic).

DEFOGGER I:
SEE FUSE BLOCK
DETAILS
DEFOGGER
CONTROL
DISTRIBUTION
-

DEFOGGER
TROUBLESHOOTING HINTS
e Try the following checks before doing the
System Check.
1. Check the PWR ACC Circuit Breaker by
operating the Power Door Locks or Power
Seats (if equipped).
2. Check the Gages Fuse by observing that the
Instrument Cluster Lights.
3. Check ground 6200 by observing that the
Cigar Lighter operates normally.
4. Check that the connectors on the Defogger
and the Defogger Timer-Relay are properly
mated.
5. If one or more of the grid lines do not heat,
refer to the Body Service Manual (Section
2) for repair procedures.
e Go to System Check for a guide to normal
operation.
a Go to System Diagnosis for diagnostic tests.
COMPONENT LOCATION Page-Figure
............ ............. Defogger Timer-Relay Behind
RH side of IIP, near ECM 201-1 1-D
..................... Fuse Block. Behind LH side
of I/P, below light switch. ...... 201-10-A
.................. 6201 (1 cavity) LH
shroud, near center access hole
.......................... 6200 Behind IIP, left of steering column ............ 201-10-16
.......................... 6322 Rear of car, near RH hatch support bracket. .... 201-15-D
.......................... S204. IIP harness, behind instrument cluster. ........ 201-10-A
.......................... S205. IIP harness, behind instrument cluster. ........ 201-10-A
.......................... S233. IIP harness, above Fuse Block. ............... 201-10-A
.......................... S327. Defogger harness, behind LR side of rear seat
SYSTEM CHECK
e Use the System Check Table as a guide to
normal operation. Refer to the diagnosis
given if other results occur. The actions must
be
pedormed in the order shown.
Tests follow in System Diagnosis.
SYSTEM CHECK TABLE -- -
ACTION NORMAL RESULT FOR DIAGNOSIS OF OTHER RESULTS
1. Turn the Ignition Switch to RUN, and de-
press the Defogger Control Switch.
2. Depress the Defogger Control Switch again
3. With the Defogger ON, depress the Defog-
ger Control OFF Switch
I
A. The switch button returns to the rest posi-
tion, and the ON Indicator in the center of the
Defogger Control lights
B. The Defogger grid removes fog from the
rear window
C. The ON Indicator and the Defogger turn
off after approximately
10 minutes
The ON Indicator and the Defogger turn on
After approximately
5 minutes, they turn off
again
The ON Indicator and the Defogger turn OFF Do
Test A
Do Test B
Do Test D
Replace the Defogger Timer-Relay
Do Test B
(Continued on next page)

DEFOGGER
SYSTEM DIAGNOSIS
Do the tests below when directed by the
System Check.
A. DEFOGGER TIMER-RELAY INPUT
VOLTAGE TEST
At: DEFOGGER TIMER-RELAY CONNECTOR
(ORN/ I Battery
BLK) &
I Ground I
(PNK/ I Battery I See 2 BLK) & I
Ground
If all the voltages are correct, go to Test
B.
1. Check the ORN/BLK (60) wire for an
open (see schematic). If the wire is OK,
check the PWR ACC Circuit Breaker.
2. Check the PNK/BLK (39) wire for an
open (see schematic). If the wire is OK,
check the Gages Fuse.
-RELAY CONNECTOR
Ignition Svvitch: RUN
A (PPLIWWT) Test Lamp
& Ground does not light See 1
If all the
results are correct, do Test D.
1. Replace the Defogger Timer-Relay.
2. Check the
BLKIWKT (150) wire for an
open (see schematic). Check that ground
6200 is clean and tight.
3. Check the LT BLU (292) wire for an open
(see schematic).
If the wire is OK, do Test
6.
4. DoTest C.
B: DEFOGGER TIMER-RELAY TEST 6: DEFOGGER CONTROL VOLTAGE
TEST
At: DEFOGGER CONTROL CONNECTOR
e lgnition Switch: RUN
Defogger Switch: ON (HOLD)
a Headlight Switch: PARK (Maximum
I C (GRY) &
D (BLK) Battery

DEFOGGER
r If all the voltages are correct, and the
Defogger still does not operate properly,
do Test D.
1. Check the PNK/BLK (39) wire for an
open (see schematic). If the wire is OK,
check the Gages Fuse.
2. Replace the Defogger Control.
3. Check the PPL/WHT (293) wire for an
open (see schematic). If the wire is OK,
do Test B.
4. Check the INST LP Fuse. Check the
GRY
(8) wire for an open (see
schematic).
5. Check the BLK (150) wire for an open
(see schematic). Check that ground
6200 is clean and tight. Replace Panel
Light if wire and ground are OK.
D: DEFOGGER TEST
With the Ignition Switch in RUN, and the
Defogger Switch pressed
ON, connect one lead
of a test lamp to ground. From inside the car,
lightly touch the other lead to each grid line,
and slowly move it along the length of the grid.
The brilliance of the test lamp bulb should
increase as the test lamp is moved from left
(Passenger's side) to right (Driver's side).
0 If the test lamp does not light along any one of
the grid lines, check
PPLIWHT (2931, PPL
(192) and BLK (192) wires to the Defogger
Control for an open
(see schematic). If OK, do
Test
E.
If the test lamp bulb shows full brilliance at
both ends of the grid, check the BLK
(1 50)
wire for an open to ground (see schematic).
e If the test lamp suddenly lights as it is moved
along the grid, a break in the continuity of the
grid line exists. Refer to the
GM Body Service
Manual for grid line repair procedure.
E: DEFOGGER LAMP TEST
CH SUPPORT ARM
Ignition Switch: RUN
LH Hatch
Support Arm
(Braided Test
Lamp
lights See
1
Wire) &
Ground
(see
schematic)
(Continued in next column) (Continued
from previous column)
See 2
Arm
(Braided
Wire) (see
schematic)
I
If all the results are correct, refer to the
GM Body Service Manual Section 2 for
grid line repair.
1. Do Test B.
2. Check the BLK (150) wire for an open
(see schematic). Check that Ground
6322 is clean and tight (see schematic).
CIRCUIT OPERATION
With the Ignition Switch in RUN, voltage
is applied to the Defogger Control. When the
Defogger Control Switch is pressed ON, volt-
age is then applied to the Defogger
Timer-
Relay. The contact closes which provides volt-
age to the ON Indicator and the Defogger.
The rear window will become warm to remove
the fog from the surface of the window.
The contact in the Defogger Timer-Relay
will stay closed until the Defogger OFF
Switch is pushed, or the timer cycle is
complete.
(Continued on next page)