stationary electromagnetic A/C clutch field coil with a
zener diode, a pulley bearing and pulley assembly,
and a clutch plate (Fig. 1). These components provide

the means to engage and disengage the A/C compres-
sor from the engine accessory drive belt.

The A/C clutch field coil and the pulley bearing

and pulley assembly are both retained on the nose of
the A/C compressor with snap rings. The clutch plate
is splined to the compressor shaft and secured with a
bolt.

CONTROLS - FRONT

24 - 13

OPERATION

The A/C compressor clutch components provide the

means to engage and disengage the A/C compressor
from the engine accessory drive belt. When the elec-
tromagnetic A/C clutch field coil is energized, it mag-
netically draws the clutch plate into contact with the
clutch pulley and drives the compressor shaft. When
the coil is not energized, the pulley freewheels on the
clutch hub bearing, which is part of the pulley.

A zener diode is connected in parallel with the

clutch electromagnetic coil. This diode controls the
dissipation of voltage induced into the coil windings
by the collapsing of the electromagnetic fields that
occurs when the compressor clutch is disengaged.
The zener diode dissipates this induced voltage by
regulating a current path to ground. This arrange-
ment serves to protect other circuits and components
from potentially damaging voltage spikes in the vehi-
cle electrical system that might occur if the voltage
induced in the clutch coil windings could not be dis-
sipated.

The compressor clutch engagement is controlled by

several components: the A/C-heater control in the
passenger compartment, the A/C pressure transducer
on the liquid line, the evaporator temperature sensor
in the HVAC housing for RS models or on the expan-
sion valve for RG models, the powertrain control
module (PCM) in the engine compartment, and the
compressor clutch relay in the integrated power mod-
ule (IPM). The PCM may delay compressor clutch

engagement for up to thirty seconds (Refer to 8 -
ELECTRICAL/ELECTRONIC

CONTROL

MOD-

ULES/POWERTRAIN

CONTROL

MODULE

DESCRIPTION - PCM OPERATION).

The A/C compressor clutch components cannot be

repaired and, if faulty or damaged, they must be
replaced.

DIAGNOSIS AND TESTING

A/C COMPRESSOR CLUTCH COIL

The air conditioning compressor clutch coil electri-

cal circuit is controlled by the powertrain control
module (PCM) through the A/C compressor clutch
relay, which is located in the integrated power mod-
ule (IPM) in the engine compartment. Begin testing
of a suspected compressor clutch coil problem by per-
forming the preliminary checks.

PRELIMINARY CHECKS

(1) If the compressor clutch will not engage, verify

the refrigerant charge level (Refer to 24 - HEATING
& AIR CONDITIONING/PLUMBING - FRONT/RE-
FRIGERANT

DIAGNOSIS

AND

TESTING

REFRIGERANT CHARGE LEVEL). If the refriger-
ant charge level is OK, go to Step 2. If the refriger-
ant charge level is not OK, adjust the refrigerant
charge as required.

(2) If the A/C compressor clutch still will not

engage, disconnect the wire harness connector for the
A/C pressure transducer and check for battery cur-
rent at the connector with the engine running and
the A/C-heater control set to the A/C mode. If OK, go
to TESTS. If not OK, refer to Body Diagnostic Proce-
dures to perform further diagnosis.

TESTS

(1) Verify the battery state of charge (Refer to 8 -

ELECTRICAL/BATTERY

SYSTEM/BATTERY

DIAGNOSIS AND TESTING).

(2) Connect an ammeter (0 to 10 ampere scale

selected) in series with the clutch coil feed terminal.
Connect a voltmeter (0 to 20 volt scale selected) to
measure voltage across the battery and the clutch
coil.

(3) With the heater-A/C control in the A/C mode

and the blower at low speed, start the engine and
allow it to run at a normal idle speed.

(4) The compressor clutch should engage immedi-

ately, and the clutch coil voltage should be within
two volts of the battery voltage. If the coil voltage is
not within two volts of battery voltage, test the
clutch coil feed circuit for excessive voltage drop. If
the compressor clutch does not engage, refer to Body
Diagnostic Procedures to perform further diagnosis.

Fig. 1 A/C Compressor Clutch

1 - BOLT
2 - CLUTCH PLATE
3 - PULLEY AND BEARING
4 - FIELD COIL
5 - SNAP RING (2)
6 - SHIM

24 - 14

CONTROLS - FRONT

A/C COMPRESSOR CLUTCH/COIL (Continued)

(5) For the acceptable A/C clutch coil current draw

specifications refer to 24 - HEATING & AIR CONDI-
TIONING - SPECIFICATIONS. Specifications apply
for a work area temperature of 21° C (70° F). If volt-
age is more than 12.5 volts, add electrical loads by
turning on electrical accessories until voltage reads
below 12.5 volts.

(a) If the compressor clutch coil current reading

is zero, the coil is open and must be replaced.

(b) If the compressor clutch coil current reading

is four amperes or more, the coil is shorted and
must be replaced.

STANDARD PROCEDURE

A/C CLUTCH INSPECTION

NOTE: The A/C clutch can be serviced in the vehi-
cle. The refrigerant system can remain fully-charged
during

compressor

clutch,

pulley

and

bearing

assembly, or coil replacement.

Examine the friction surfaces of the clutch pulley

and the clutch plate for wear (Fig. 2). The pulley and
plate should be replaced if there is excessive wear or
scoring.

If the friction surfaces are oily, inspect the shaft

and nose area of the A/C compressor for refrigerant
oil. If refrigerant oil is found, the compressor shaft
seal is leaking and the A/C compressor must be
replaced.

Check the clutch pulley bearing for roughness or

excessive leakage of grease. Replace the pulley and
bearing assembly, if required.

A/C CLUTCH BREAK-IN

After a new A/C compressor clutch has been

installed, cycle the compressor clutch approximately
twenty times (five seconds on, then five seconds off).
During this procedure, set the A/C-heater controls to
the A/C Recirculation Mode, the blower motor in the
highest speed position, and the engine speed at 1500
to 2000 rpm. This procedure (burnishing) will seat
the opposing friction surfaces and provide a higher
compressor clutch torque capability.

REMOVAL

NOTE: The compressor clutch can be serviced in
the vehicle. The refrigerant system can remain fully-
charged during compressor clutch, pulley, or coil
replacement.

(1) Disconnect and isolate the negative battery

cable.

(2) Remove the accessory drive belt (Refer to 7 -

COOLING/ACCESSORY

DRIVE/DRIVE

BELTS

REMOVAL).

(3) Raise and support the vehicle.
(4) Disconnect the engine wire harness connector

from the clutch coil connector located on the top of
the A/C compressor.

(5) On models with the 3.3L and 3.8L engines, dis-

engage the engine wire harness connector retainer
from the bracket located on the top of the A/C com-
pressor.

(6) On models with the 2.4L, 2.5L and 2.8L

engines, remove all of the compressor mounting bolts
except the upper left (rear of the A/C compressor),
which should only be loosened. Allow the front (pul-
ley end) of the A/C compressor to tilt downward far
enough to access the clutch for removal, then tighten
the loosened upper left compressor mounting bolt.

(7) On models with the 3.3L and 3.8L engines,

remove the two bolts and two nuts that secure the
A/C compressor to the engine. Disengage the mount-
ing ear at the front of the A/C compressor from the
stud on the engine, allow the front (pulley end) of the
A/C compressor to tilt downward far enough to access
the clutch for removal, then reinstall and tighten the
upper left compressor mounting bolt.

(8) Remove the compressor shaft bolt (Fig. 3). A

band-type oil filter wrench or a strap wrench may be
used to secure the clutch during bolt removal.

Fig. 2 Clutch Plate and Shim(s)

1 - A/C COMPRESSOR SHAFT
2 - CLUTCH PLATE
3 - SHIM

CONTROLS - FRONT

24 - 15

A/C COMPRESSOR CLUTCH/COIL (Continued)

(9) Tap the clutch plate lightly with a plastic mal-

let to release it from the splines on the compressor
shaft. Remove the clutch plate and shim(s) from the
compressor shaft (Fig. 4).

NOTE: Use care not to lose any of the shim(s).

CAUTION: Do not pry between the clutch plate unit
and the pulley to remove the clutch plate from the
compressor shaft as this may damage the clutch
plate.

(10) Using snap ring pliers (Special Tool C-4574 or

equivalent), remove the external snap ring that
secures the pulley to the front cover of the A/C com-
pressor, then slide the pulley off of the compressor
(Fig. 5).

(11) Remove the screw that secures the clutch coil

wire lead connector bracket and ground clip to the
top of the compressor housing.

(12) Using snap ring pliers (Special Tool C-4574 or

equivalent), remove the external snap ring that
secures the clutch coil to the front cover of the com-
pressor housing, then slide the clutch coil off of the
A/C compressor (Fig. 6).

INSTALLATION

(1) Align the dowel pin on the back of the clutch

coil with the hole in the compressor front cover and
position the clutch coil onto the A/C compressor. Be

certain that the clutch coil pigtail wires are properly
oriented and routed so that they are not pinched

Fig. 3 A/C Compressor Shaft Bolt

1 - BOLT
2 - COMPRESSOR CLUTCH PLATE

Fig. 4 Clutch Plate and Shim(s)

1 - A/C COMPRESSOR SHAFT
2 - CLUTCH PLATE
3 - SHIM

Fig. 5 Clutch Pulley Snap Ring

1 - SNAP RING
2 - SNAP RING PLIERS
3 - CLUTCH PULLEY AND BEARING

24 - 16

CONTROLS - FRONT

A/C COMPRESSOR CLUTCH/COIL (Continued)

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