A/C Compressor Clutch Description; Diagnosis And Testing; A/C Compressor Clutch Coil - Jeep KJ 2005 Service Manual

KJ
A/C COMPRESSOR CLUTCH
DESCRIPTION
The A/C compressor clutch assembly consists of a
stationary electromagnetic A/C clutch field coil, pul-
ley bearing and pulley assembly, clutch plate and
shims (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 keyed or splined to the compressor shaft and
secured with a nut.
Fig. 1 A/C Compressor Clutch - Typical
1 - CLUTCH PLATE
2 - SHAFT KEY (SOME MODELS)
3 - PULLEY AND BEARING
4 - CLUTCH COIL
5 - CLUTCH SHIMS
6 - SNAP RING
7 - SNAP RING
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 following:
• A/C-heater mode control
• A/C clutch relay
• A/C pressure transducer (gasoline engines)
• A/C high pressure switch (diesel engine)
• A/C low pressure switch
• Powertrain control module (PCM) or engine con-
trol module (ECM) (depending on application)
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) or
the engine control module (ECM) (depending on
engine application) through the A/C clutch relay.
Begin testing of a suspected 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) or the
engine control module (ECM) (depending on engine
application), 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 or 3.7L gas-
oline engine, if the A/C compressor clutch still will
not engage, disconnect the wire harness connector
from the A/C pressure transducer and check for bat-
tery current at the connector with the engine run-
ning 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 Procedures to perform further diagnosis.
On models equipped with the 2.8L diesel engine, go
to TESTS.
TESTS
(1) Verify the battery state of charge (Refer to 8 -
ELECTRICAL/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-
tion for testing of the compressor clutch circuit and
CONTROLS 24 - 11
SYSTEM/BATTERY -