1988 PONTIAC FIERO air conditioning

AIR CONDITIONING: COMPRESSOR CONTROLS
660, MANUAL
The A/C Compressor Control Relay is oper-
ated by the ECM. When the ECM receives the
A/C ON signal at terminal B8, it grounds termi-
nal A2 energizing the relay. When the relay is
energized, voltage is applied to the
AlC Com-
pressor Clutch through the contacts of the
relay.
If the ECM determines that engine load
should be reduced, such
as during full throttle,
the
A/C Compressor Control Relay is de-ener-
gized, which removes voltage from the Ale
Compressor Clutch, thus removing the Ale
load from the engine.
V8 VIN F, V8 VIN 8
From the A/C Control Read, voltage is
applied to the
A/C Compressor Clutch through
the Pressure Cycling Switch and the
A/C High
Pressure Cut-Out Switch. The Pressure
Cycling
Switch is normally closed but opens when
refrigerant pressure drops below
172kPa (25
psi).
It closes again when refrigerant pressure
rises enough that additional cooling is required.
This action causes the
A/C Compressor to cycle
on and off so that the evaporator temperature
does not drop low enough to cause icing. The
A/
C High Pressure Cut-Out Switch opens if
refrigerant pressure rises to a point that is too
high for normal operation.
When voltage is applied to the Compressor
Clutch, it is also applied to the ECM at terminal
B8 on connector Cl. The ECM will than
increase the engine idle speed while the
Ale
Compressor Clutch is engaged.
V8 VIM E
From the Ale Control Head, voltage is
applied to the
A/C Compressor Clutch through
the Pressure Cycling Switch and the
AIC High
Pressure Cut-Out Switch. The Pressure Cycling
Switch is normally closed but opens when
refrigerant pressure drops below 172
kPa (25
psi).
It closes again when refrigerant pressure
rises
enough that additional cooling is required.
This action causes the
AIC Compressor to cycle
on and off so that the evaporator temperature
does not drop low enough the cause icing. The
A/C High Pressure Cut-Out Switch opens if
refrigerant pressure becomes too high for nor-
mal operation.
When voltage is applied to the Compressor
Clutch, it is also applied to the Computer Com-
mand Control to signal the ECM to maintain
normal engine idle speed while the
Ale Com-
pressor Clutch is engaged.

% AIR CONDITIONING: AIR DELIVERY
660, MANUAL
CHECK - VALVE -
VACUUM
SOURCE TO
CRUISE
CONTROL

AIR CONDITIONING: AlR DELIVERY
660, MANUAL
TROUBLESHOOTING HINTS
Try the following checks before doing System
Diagnosis.
1. Cheek for manifold vacuum to the vacuum
tank at the BLACK hose from the engine and
at the VIOLET hose to the
A/C Control
Head.
2. Check the operation of the Temperature
Valve by moving the Temperature Selector
rapidly back and forth several times. Listen
for the valve to strike the stop at each end of
its travel.
If the sound indicates that the
valve is not fully closing or opening, check
the mechanical linkage between the valve
and the Temperature Selector.
3. Check that Heater Water Bypass Valve
operates when Temperature Selector is
moved to maximum cold position.
Go to the AlC System Check in 8A-62 for a
guide to normal operation and diagnostic ref-
erences for the entire
AIC System.
r Go to Systern Diagnosis to isolate air delivery
conditions.
SYSTEM DIAGNOSIS
Engine vvarm and running at idle.
If air flow does not come from the proper
outlets under one or more operating modes,
at least one of the air valves is not moving to
the proper position.
Check the operation of the air valves using
the following chart. Put Blower Switch in
HI
to give a strong flow of air.
COMPONENT LOGATlORl Page-Figure
Check Valve.
. . . . . . . . . . . . . . . . . . . . Behind engine, to right of master brake cylinder . 201-15-A
HeatIDefrost Vacuum Actuator . . . . Behind IIP, on LN side of plenum . . . . . . . . . . . . . 201-14-6
Lower Mode Vacuum Actuator
. . . . . Behind I/P, on LH lower side of plenum . . . . . . . . 201-14-C
Recirculating-Outside Air Vacuurn
Actuator (Manual) . . . . . . . . . . . . . . Behind IIP, on RH side of plenum. . . . . . . . . . . . . 201-14-6
Upper Mode Vacuum Actuator
. . . . . Behind I/P, on LN side of plenum . . . . . . . . . . . . . 201-14-6
Vacuum Tank
. . . . . . . . . . . . . . . . . . . Lower LIH front corner of engine compartment . . 201-15-A
AIR VALVE POSlTlON TABLE * Additional tests of the Ale Vacuum System
are given in Section
1 B.
GIWCUiT OPEMTIOIU
The air valves in the air conditioning system
are operated by mechanical and vacuum con-
trols. There are no electrical circuits. The func-
tions of the air valves and
A/C Evaporator Core
are described below.
Temperature Valve
The Temperature Valve is mechanically
linked to the temperature selector in the
AIC
Control Head. With the selector in Cold, the
valve is in the cold position. This prevents air
from blowing across the Heater Core. With the
selector in any other position, some or
all of the
air blows across the Heater Core providing con-
tinuous temperature control.
(Continued on next page)

3 AIR CONDITIONING: BLOWER CONTROLS a, P
C67, ELECTRONlC I
DRIVER
INFORMATION
CENTER

AIR CONDITIONING: BLOWER CONTROLS
TROUBLESHOOTING NlNTS
a Try the following checks before doing the
System Diagnosis
.
1 . Check the HTR A/C Fuse by visual inspection .
2 . Check that 6112 is clean and tight .
3 . Check that Blower Motor connectors and
Blower Relay are mated correctly and firmly
seated
.
a Go the the AIC Systern Check in 813-62 for a
guide to normal operation
.
Go to Systern Diagnosis in this section for
diagnostic tests
.
SYSTEM DIAGNOSIS
Do the tests listed for your symptom in the
Symptom Table below
.
Tests follow the Symptom Table .
COMPONENT LOCATION Page-Figure
Blower High Speed Relay
.......... RH front of dash. near Blower Motor ..........
Blower Motor (With AIC) .......... RH front of dash ...........................
Blower Resistors (With AIC) ....... RH front of dash. behind strut tower ..........
...................... Fuse Block
Behind LH side of IIP. below light switch .......
............ Fusible Link B (VIN E) Lower RH side of engine. at Starter Solenoid ....
Fusible Link B (VIN F) (VIN 8) ..... Lower RH side of engine. at Starter Solenoid ....
............ Fusible Link B (VIN S) Lower RN side of engine. at Starter Solenoid ....
................ Low Blower Relay RH front of dash. near Blower Motor ..........
........................ ................. C102 (4 cavities) Center
front of dash
................... ........................ C115 (1 cavity) Center
front of dash
................. ............. C215 (3 cavities) Center
of IIP. behind AlC control
................. ............. 6224 (6 cavities) Center
of IIP. behind Ale control
................... .................... 6112 (VIN E) Rear of LH cylinder head
............. .................... 6112 (VIN F) (VIN 8) Rear of LH cylinder head
.................... .................... 6112 (VIN S) Rear
of LN cylinder head
.......................... ............ 6200 Behind I/P. left of steering column
........................... Slll Engine harness. RN rear of engine compartment
.................... ............. S117 (VIN E) Engine harness. RH front of dash
............. ....... S117 (VIN F) (VIN 8) Engine harness. top center rear of engine
........................... ................ S153 AIC harness. RH front of dash
........................... ......... S205 IIP harness. behind instrument cluster
........................... S225 IIP harness. behind instrument cluster .........

AIR CONDITIONING: BLOWER CONTROLS
C67, ELECTRONIC
SYMPTOM TABLE 4: BLOVVER MOTOR TEST
Measure: VOLTAGE
At: BLOWER MOTOR CONNECTORS
(Disconnected)
Conditions:
r Ignition Switch: RUN
NC Mode: VENT
e Blower Switch: HI
I C2:zt;)d& I Battery I See 1 I
Measure
Between
& Battery See 2
If the voltages are correct, but the Blower
does not
run, install a new Blower Motor.
Correct
Voltage
1. Check PPL (65) wire for an open. If wire is
good, do Tests B and
D.
For
Diagnosis
1 2. Check BLK (150) wire for an open and
ground
6112 is clean and tight.
B: BLOWER HIGH SPEED RELAY TEST
(TABLE
11
I D(RED) Ground & I Battery I See 1 I
Measure: VOLTAGE
AT: BLOWER HIGH SPEED RELAY
CONNECTOR (Disconnect)
Conditions:
ignition Switch: RUN
r AIC Mode: VENT
r Blower Switch: HI
I (PPL) & 1 Battery
Ground I See 2 I
For
Diagnosis
Measure
Between
a If voltages are correct, proceed to Table 2.
1. Check RED (2) wire for an open back to
F'usible Link B.
2. Check PPL (101) wire for an open. If wire is
good, do Test
C.
3. Check ORN (52) wire for an open. If wire is
good, do Test
D.
Correct
Voltage
(ORN) &
Ground
(Continued on next page)
Battery
See 3

AIR CONDITIONING: BLOWER CONTROLS
(Continued from previous page)
B: BLOWER HIGH SPEED RELAY TEST
(TABLE
2)
Measure: RESISTANCE
AT: BLOWER
HIGH SPEED RELAY
CONNECTOR (Disconnected)
Conditions:
o lgnition Switch: OFF
o Negative Battery
Terminal: DISCONNECTED
( Measure I Correct I For 1
Between I Resistance I Diagnosis
B (BLK) & 0 ohms
Ground
Ground
3 ohms
0 If voltages in Table 1 and resistances in
Table 2 are correct, but Blower Relay does
not operate or runs
all the time, replace
the Blower Relay.
1. Check BLK (150) wire for an open.
6: BLOVVER RESlSTORS TEST D: BLOVVER SWITCH TEST (TABLE 1)
2.
Check PPL (65) wire for an open. If wire is
good, recheck measurements made in
Test A.
Measure: RESISTANCE
At: BLOWER RESISTORS CONNECTOR
(Disconnected)
Condition:
Ignition Switch: OFF
Measure
Between
A&C
C&D
D&B
OR CONNECTOR
(Disconnected)
lgnition Switch: RUN
AIC Mode: VENT
Blower Switch: M2
If
resistances are correct, Blower Resistors
are operating normally. Return to Symptom
Table.
1. Install new Blower Resistors.
Correct
Resistance
1.5 rt. 1 ohm
0.7
+ .5 ohm
0.2
rt. .l ohm
D (LT BLU) &
Ground
For
Diagnosis
See 1
See 1
See 1
If all voltages are correct, go to Table 2.
1. Check BRNIWNT (64) wire for an open. If
wire
is good, do Test E. (see schematic).
2. If battery voltage is present, check for a
wire to wire short to voltage. If wire is good,
replace the Blower Switch.
3. Check TAN (63) wire for an open.
4. Check LT BLU (72) wire for an open.
5. If voltage is present at terminal A but is
not present at either terminals C or
D,
check the BRNIWHT (64) wire for an open
between the Blower Resistor terminal A
and the AlC Control Head terminal E.
Battery See 4 and 5

AIR CONDITIONING: BLOWER CONTROLS
I): BLOWER SWITCH TEST (TABLE 23
Measure: VOLTAGE
At: BLOWER
HIGH SPEED RELAY
CONNECTOR
(Disconnected)
Conditions:
e lgnition Switch: RUN
e NC Mode: VENT
@ Blower Switch: M2
I E(ORN)& 1 0 volts
Ground
Measure
Between
I . Blower Switch: HI I
Correct
Voltage
If all voltages are correct, Blower Switch is
operating normally. Return to Symptom
'Pable.
1. If voltage is present, check ORN (52) wire
for a wire to wire short to voltage. If wire is
good, replace Blower Switch.
2. Check ORN (52) wire for an open. If wire is
good, replace Blower Switch.
For
Diagnosis
(ORN) &
Ground
E: LW BLOWER RELAY TEST
Measure: VOLTAGE
At: LOW BLOWER
RELAY
(Disconnected)
Conditions:
e lgnition Switch: RUN
1 a NC Mode: OFF
Battery See 2
I A Ground (BRN) & I Battery I See 1 and 2 1
Measure
Between
I I Battery I see 3 I
Correct
Voltage
(BRN) &
Ground
For
Diagnosis
1 r A/C Mode: All modes except OFF I
Battery
B (BRN) & C
(GRY)
See 1 and 2
If all voltages are correct, but blower runs
in
Ale OFF Mode, or no voltages are pre-
sent in other tests, replace the Low
Blower Relay.
1. Check for an open in BRN (50) wire.
Battery
B (BRN) & C
(GRY
2. If voltages are incorrect at both terminals
A and B, check Blower Fuse and BRN (50)
wire.
3. Check for open in BRNNVHT (64) wire.
4. Check for open in GRY or LT GRNIBLK
(990) wires. If wires are good, do Test F.
5. Check for short to ground in GRY or LT
GRNIBLK (990) wires. If wires are good, re-
place the
A/C Control Head. See
4
F: NG MODE SELECTOR BLOWER
CONTROL TEST
, volts See 5
Measure: VOLTAGE
At: AIG CONTROL HEAD CONNECTOR C1
and 62
(Connected)
Conditions:
e lgnition Switch: RUN
a MC Mode: OFF
I ~EEZ I 0 volts 1 See 2 1
N (BLK) 61 &
Ground
Ground
For
Diagnosis I Measure
Betvveen
I $2 I 0 volts I See 3 1
Correct
bltage
volts
Ground See
1
A/C Mode:
All positions except OFF.
A (LT GW
BLK) 61 & Battery
Ground
@ If all voltages are correct, A/C Mode Selec-
tor and Low Blower Relay are operating
normally. Return to Symptom
'Pable.
E (BRNNVHT)
62 & Ground
1. If voltage is present, check BLK (150) wire
for an open. Check that
6200 is clean and
tight.
2. If voltage is present, replace
A/C Control
Head.
3. If voltage is present, replace Low Blower
Relay.
(Continued on next page)
Battery See 5