DRIVEABILITY AND EMISSIONS 2.8L (VIN S) 6E3-C40-1
SECTION CIO
ECM CONTROLLED AIR CONDlTlOlUlNG
CONXENTS
GENERAL DESCRIPTION ................ C10-1 DIAGNOSIS ......................... C10-1
OPERATION ....................... C10-1 ON-CARSERVICE ..................... C10-1
GENERAL DESCRIPmON
In order to improve idle quality and wide open
throttle performance, the
NC compressor is controlled
by the ECM.
There are two different types of
AJC 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
NC is
requested, 12V power is supplied to the pressure
cycling switch and to the
NC power relay. The ECM
controls the
A/C clutch by energizing the A/C control
relay. This allows the
EChI to incrctlse idle speed
before turning on
NC to improve idle quality. 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
NC circuit.
DIAGNOSIS
CHART C-10 should be used for diagnosing the
electrical portion of the
A/C circuit. Section "1R"
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 NC
components, refer to Section
" 1" of the service manual.
