Through - Pontiac Fiero 1988 Service Manual

8E3-C1Q-2 D R I V E A B I L I T Y A N D E M I S S I O N S - FUEL I N J E C T I O N (PORT)
A/C
CONTROL PROMT
SWITCH BULKHEAD
A/C FUSE
A/C
CLUTCH
CONTROL
RELAY
GRN 66
PRESSURE
CYCLING
SWITCH
BLU
7 » BRN ^ k j u j u u r * ^
D 1 ' B
BLK 150
n
A/C POWER RELAY
50 DK GRN
FRONT
V B U L K H E A D
(D)&M>. CONNECTOR
TO BLOWER
^ SWITCH
ECM
# - 67 LT BLU
— 459 DKBLU
59 DK
GRN
RELAY RELAY
HARNESS END
CONNECTOR VIEW
5-26-87
A/C CLUTCH
A/C REQUEST
~~ SIGNAL
18
A/C REQUEST
~~ SIGNAL
CI
A/C REQUEST
~~ SIGNAL
CI
A/C CLUTCH "=
CONTROL
A/C CLUTCH "=
CONTROL
HIGH PRESSURE
CUT-OUT SWITCH
11-19-86
*6S 2683-6E
CHART C-10
A/C CLUTCH CONTROL DIAGNOSIS
2.8L "P" SERIES (PORT)
Circuit
D e s c r i p t i o n :
Electronic control module (ECM) control of the A/C clutch improves idle quality and performance by;
• delaying clutch apply until the idle air rate is increased.
• releasing clutch when idle speed is too low.
• releasing clutch at wide open throttle.
• smooths cycling of the compressor by providing additional fuel at the instant clutch is applied.
Voltage is supplied to the A/C Clutch Control relay on CKT 50 when the A/C power relay is energized by the
A/C Control Switch. Also, when the A/C is turned "ON," voltage is supplied to the A/C relay coil on CKT 67
through the closed pressure cycling switch. This same voltage is supplied as a signal to ECM pin B8. After a
time delay of about 1/2 second the ECM will ground terminal "C2," CKT 458, and close the A/C relay contacts.
When relay is energized battery voltage from CKT 50 is supplied to the A/C clutch through the relay and
CKT 59.
Test Description:
Numbers below refer to circled
numbers on the diagnostic chart.
1. The ECM will only energize the A/C relay, when
the engine is running. This test will determine if
the relay, or CKT 459, is faulty.
2. In order for the clutch to properly be engaged, the
low pressure switch must be closed to provide 12
volts to the relay, and the high pressure switch
must be closed, so the A/C request (12 volts) will
be present at the ECM.
3. Determines if the signal is reaching the ECM on
CKT 366 from the A/C control panel. Signal
should only be present when the A/C mode or
defrost mode has been selected.
5.
A short to ground in any part of the A/C request
circuit, CKT 67 to the relay, CKT 902 to the A/C
clutch, or the A/C clutch, could be the cause of the
blown fuse.
With the engine idling and A/C "ON", the ECM
should be grounding CKT 459, which should cause
the test light to be "ON".
D i a g n o s t i c A i d s :
If complaint was insufficient cooling, the problem
may be caused by a inoperative cooling fan. The
engine cooling fan should turn "ON", when A/C is
"ON". If not, see Section "8A" for fan diagnosis.