Pontiac Fiero 1988 Service Manual page 570

D R I V E A B I L I T Y A N D E M I S S I O N S - F U E L I N J E C T I O N (TBI) 6 E 2 - C 1 0 - 1
SECTION C10
ECM CONTROLLED AIR CONDITIONING
CONTENTS
G E N E R A L D E S C R I P T I O N . . .
OPERATION
C10-1 D I A G N O S I S
C10-1
O N - C A R S E R V I C E
C10-1
C10-1
GENERAL DESCRIPTION
In order to improve idle quality and wide open
throttle performance, the A/C compressor is controlled
by the ECM.
There are two different types of A/C systems used
in GM vehicles. One is referred to as C.C.O.T. (cycling
clutch orifice tube), which uses a fixed displacement
compressor. The other type of system uses a
compressor with a variable displacement, and is
referred to as the V-5 type system. The V-5 type meets
A/C requirements without cycling. For descriptions of
both types, and an explanation of the components
used, refer to Section "IB" of the service manual.
O P E R A T I O N : V - 5 Type (2.5L)
This system consists of a low pressure switch, a
high pressure cut-out switch, a control relay, and the
compressor.
The low pressure switch is closed, when there is
sufficient system pressure (depending on refrigerant
charge and ambient temp.). When A/C control switch
is "ON", and low pressure switch is closed, a signal is
sent to the ECM which then turns "ON" the cooling
fan.
A C RELAY
A N D
CONNECTOR
FUEL PUMP RELAY
A N D CONNECTOR
8S 4376
The high pressure cut-out switch (normally
closed), opens when the head pressure gets too high.
This disables the A/C clutch, before damage can occur
to the system.
The A/C control relay is controlled by the ECM, so
that the ECM can increase idle speed before turning
on the clutch, to disable the clutch during WOT, or
during high power steering loads.
See appropriate C-10 chart for specific wiring and
circuit description.
DIAGNOSIS
CHART C-10 should be used for diagnosing the
electrical portion of the A/C circuit. Section IB should
be used for diagnosing the refrigerant portion of the
system.
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system, as it has the ability to read the A/C request
input to the ECM, as well as displaying when the
ECM has commanded the A/C clutch "ON"
ON-CAR SERVICE
For removal and replacement procedures of A/C
components, refer to Section "1" of the service manual.
Figure C10-1 A/C Relay. 2.5L
[ T 1
LOW PRESSURE SWITCH
FT] HIGH PRESSURE SWITCH
8S 4377
Figure C10-2 A/C Press. Switches, 2.5L