stationary electromagnetic A/C clutch field coil, a pul-
ley bearing and pulley assembly, and a clutch plate
(Fig. 1). These components provide the means to
engage and disengage the A/C compressor 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.

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/C clutch engagement is controlled by the follow-

ing:

• A/C-heater mode control

• A/C clutch relay

• A/C high pressure switch

• A/C low pressure switch

• Powertrain control module (PCM)
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 A/C compressor clutch coil electrical circuit is

controlled by the powertrain control module (PCM)
through the A/C clutch relay. Begin testing of a sus-
pected compressor clutch coil problem by performing
the preliminary checks.

PRELIMINARY CHECKS

(1) If no diagnostic trouble codes (DTCs) are found

in the powertrain control module (PCM), go to Step
2. If any DTCs are found, repair as required.

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

engage, verify the refrigerant charge level (Refer to
24 - HEATING & AIR CONDITIONING/PLUMBING
- DIAGNOSIS AND TESTING - REFRIGERANT
SYSTEM LEAKS). If the refrigerant charge level is
OK, go to Step 3. If the refrigerant charge level is not
OK, adjust the refrigerant charge as required.

(3) On models equipped with the 2.4L engine, if

the A/C compressor clutch still will not engage, dis-
connect the wire harness connector for the A/C pres-
sure transducer and check for battery current 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 the Body Diagnostic Pro-
cedures to perform further diagnosis. On models
equipped with the 4.0L engine, go to TESTS.

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 A/C-heater control in the A/C mode

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

(4) The A/C compressor clutch should engage

immediately, and the clutch coil supply voltage
should be within two volts of the battery voltage. If
the coil supply voltage is OK, go to Step 5. If the coil
supply voltage is not within two volts of battery volt-
age, test the clutch coil feed circuit for excessive volt-
age drop and repair as necessary. If there is no
voltage reading at the clutch coil, use a DRB III

scan tool and refer to appropriate diagnostic informa-

Fig. 1 A/C Compressor Clutch

1 - BOLT
2 - CLUTCH PLATE
3 - PULLEY AND BEARING
4 - FIELD COIL
5 - SNAP RING
6 - SNAP RING
7 - SHIMS

CONTROLS

24 - 11

tion for testing of the compressor clutch circuit and
PCM control. The following components must be
checked and repaired as required before you can com-
plete testing of the clutch coil:

• Fuses in the fuse block and the power distribu-

tion center (PDC)

• A/C-heater mode control

• A/C clutch relay

• A/C High pressure switch (4.0L engine)

• A/C Low pressure switch

• Powertrain control module (PCM)
(5) The A/C compressor clutch coil is acceptable if

the current draw is 2.0 to 3.7 amperes. Specifications
apply for a work area temperature of 21° C (70° F). If
voltage is more than 12.5 volts, add electrical loads
by turning on electrical accessories until voltage
reads below 12.5 volts.

(a) If the A/C clutch coil current reading is zero,

the coil is open and must be replaced.

(b) If the A/C clutch coil current reading is above

specifications, the coil is shorted and must be
replaced.

STANDARD PROCEDURE

DIODE REPLACEMENT

(1) Disconnect and isolate the negative battery

cable.

(2) Locate the diode in the A/C clutch wire harness

and remove the protective covering.

(3) Remove the diode from the wire harness while

paying attention to the current flow direction (Fig. 2).

(4) Remove the insulation from the wires in the

harness. Only remove enough insulation to solder in
the new diode.

(5) Install the new diode in the harness, making

sure current flow is correct. If necessary refer to the
appropriate wiring diagram for current flow.

CAUTION: To prevent damage to the diode and wir-
ing, DO NOT use acid core solder.

(6) Solder the connections together using rosin

core type solder only.

(7) Tape the diode to the harness using electrical

tape making, sure the diode is completely sealed
from the elements.

(8) Reconnect the negative battery cable, and test

A/C clutch operation.

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. 3). 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 battery negative

cable.

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

COOLING/ACCESSORY

DRIVE/DRIVE

BELTS

REMOVAL) and (Refer to 7 - COOLING/ACCES-
SORY DRIVE/DRIVE BELTS - REMOVAL).

Fig. 2 Diode Identification

1 - CURRENT FLOW
2 - BAND INDICATES CURRENT FLOW
3 - DIODE AS SHOWN IN WIRE DIAGRAMS

24 - 12

CONTROLS

A/C COMPRESSOR CLUTCH (Continued)

(3) Remove the bolt that secures the compressor

clutch to the compressor shaft (Fig. 4). A band-type
oil filter wrench may be used to secure the clutch
during bolt removal.

(4) Tap the clutch plate with a plastic mallet to

release it from the splines on the compressor shaft.
Remove the clutch plate and shim(s) from the com-
pressor shaft (Fig. 5).

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

CAUTION: Do not use screwdrivers between the
clutch plate assembly and pulley to remove front
plate as this may damage the front plate assembly.

(5) Remove the external snap ring that secures the

compressor clutch pulley to the nose of the compres-
sor front housing with snap ring pliers (Special Tool
C-4574) or equivalent and slide the pulley assembly
off of the compressor (Fig. 6).

Fig. 3 Clutch Plate and Shim(s)

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

Fig. 4 A/C Compressor Shaft Bolt

1 - COMPRESSOR CLUTCH PLATE
2 - COMPRESSOR SHAFT BOLT

Fig. 5 Clutch Plate and Shim(s)

1 - COMPRESSOR SHAFT
2 - CLUTCH PLATE
3 - CLUTCH PLATE SHIM

Fig. 6 Pulley Snap Ring

1 - SNAP RING

CONTROLS

24 - 13

A/C COMPRESSOR CLUTCH (Continued)

Content .. 584 585 586 587 ..