Pontiac Fiero 1988 Service Manual page 706

DRIVEABILITY AND EMISSIONS - FUEL INJECTION (PORT) 6E3-C10-1
SECTION C10
ECM CONTROLLED AIR CONDITIONING
CONTENTS
GENERAL DESCRIPTION . . . . . . . . . . . . . . . . C10-1
OPERATION
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GENERAL DESCRIPTION
In order to improve idle quality and wide open
throttle performance, the A/C compressor is controlled
by the electronic control module (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.
OPERATION
The 2.8L engine uses the C.C.O.T. type A/C
system, and is controlled by the ECM. When A/C is
requested, 12V power is supplied to the pressure
cycling switch and to the A/C power relay. The ECM
controls the A/C clutch by energizing the A/C control
relay. This allows the ECM to increase idle speed
before turning on A/C to improve the quality.
The low pressure switch, mounted in the
compressor, is closed when the system contains a
sufficient refrigerant charge. This switch opens, when
pressure is less than about 40 psi (276 kPa).
The high pressure cut-out switch (normally
closed) opens when head pressure gets too high. This
disables the A/C clutch, before damage can occur to
the system. This switch opens, when pressure is
greater than about 440 psi (3034 kPa).
See CHART C-10 for diagnosis and wiring
diagram of the electrical portion of the A/C circuit.
DIAGNOSIS
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ON-CAR SERVICE
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C10-1
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.
The "Scan" tool will be used in diagnosing the
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.
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F U E L PUMP R E L A Y
F T ]
E C M H A R N E S S -
C O N N E C T O R T O F U E L P U M P
E E A / C C O N T R O L R E L A Y 4S 0 5 5 9 - 6 E
Figure C 1 0 - 1 A/C Control Relay