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

When the clutch coil is energized, it magnetically

draws the clutch into contact with the pulley and
drives the compressor shaft. When the coil is not
energized, the pulley freewheels on the clutch hub

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24 - 9

bearing, which is part of the pulley. The compressor
clutch and coil are the only serviced parts on the
compressor.

A/C compressor clutch engagement is controlled by

the following components:

• A/C-heater mode control switch

• A/C low pressure switch

• A/C high pressure switch

• A/C compressor clutch relay

• Powertrain Control Module (PCM)
The PCM may delay compressor clutch engage-

ment for up to thirty seconds.

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. The A/C clutch coil can
be tested by either measuring cluch field coil resis-
tance or by measuring current draw. Begin testing of
a suspected compressor clutch coil problem by per-
forming the preliminary checks.

PRELIMINARY CHECKS

(1) If the A/C compressor clutch will not engage,

check for diagnostic trouble codes (DTCs) in the A/C-
heater control and the powertrain control module
(PCM). If no diagnostic trouble codes (DTCs) are

found in the A/C-heater control or the 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 COIL CURRENT DRAW TEST. If the
refrigerant charge level is not OK, adjust the refrig-
erant charge as required.

COIL CURRENT DRAW TEST

(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.

(5)

Refer to 24 - HEATING & AIR CONDITION-

ING - SPECIFICATIONS for the acceptable A/C
clutch coil current draw. 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

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.

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

24 - 10

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A/C COMPRESSOR CLUTCH COIL (Continued)

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

for the compressor clutch coil from the clutch coil pig-
tail wire connector on the top of the A/C compressor.

(5) Remove the bolts that secure the A/C compres-

sor to the engine and support the A/C compressor.

(6) 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.

(7) 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.

(8) 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 compres-
sor, then slide the pulley off of the compressor (Fig.
5).

Fig. 2 Clutch Plate and Shim(s)

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

Fig. 3 A/C Compressor Shaft Bolt

1 - BOLT
2 - COMPRESSOR CLUTCH PLATE

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A/C COMPRESSOR CLUTCH COIL (Continued)

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