2002 JEEP GRAND CHEROKEE four wheel drive

Diagnosis of these problems should always begin
by checking the easily accessible variables: fluid level
and condition, gearshift cable adjustment. Then per-
form a road test to determine if the problem has been
corrected or if more diagnosis is necessary. If the
problem persists after the preliminary tests and cor-
rections are completed, hydraulic pressure checks
should be performed.
DIAGNOSIS AND TESTING - PRELIMINARY
Two basic procedures are required. One procedure for
vehicles that are drivable and an alternate procedure for
disabled vehicles (will not back up or move forward).
VEHICLE IS DRIVABLE
(1) Check for transmission fault codes using DRBt
scan tool.
(2) Check fluid level and condition.
(3) Adjust gearshift cable if complaint was based
on delayed, erratic, or harsh shifts.
(4) Road test and note how transmission upshifts,
downshifts, and engages.
(5) Perform stall test if complaint is based on slug-
gish acceleration. Or, if abnormal throttle opening is
needed to maintain normal speeds with a properly
tuned engine.
(6) Perform hydraulic pressure test if shift prob-
lems were noted during road test.
(7)
Perform air-pressure test to check clutch operation.
VEHICLE IS DISABLED
(1) Check fluid level and condition.
(2)
Check for broken or disconnected gearshift cable.
(3) Check for cracked, leaking cooler lines, or loose
or missing pressure-port plugs.(4) Raise and support vehicle on safety stands,
start engine, shift transmission into gear, and note
following:
(a) If propeller shaft turns but wheels do not,
problem is with differential or axle shafts.
(b) If propeller shaft does not turn and transmis-
sion is noisy, stop engine. Remove oil pan, and
check for debris. If pan is clear, remove transmis-
sion and check for damaged driveplate, converter,
oil pump, or input shaft.
(c) If propeller shaft does not turn and transmis-
sion is not noisy, perform hydraulic-pressure test to
determine if problem is hydraulic or mechanical.
DIAGNOSIS AND TESTING - ROAD TESTING
Before road testing, be sure the fluid level and con-
trol cable adjustments have been checked and
adjusted if necessary. Verify that all diagnostic trou-
ble codes have been resolved.
Observe engine performance during the road test.
A poorly tuned engine will not allow accurate analy-
sis of transmission operation.
Operate the transmission in all gear ranges. Check
for shift variations and engine flare which indicates
slippage. Note if shifts are harsh, spongy, delayed,
early, or if part throttle downshifts are sensitive.
Slippage indicated by engine flare, usually means
clutch, overrunning clutch, or line presure problems.
A slipping clutch can often be determined by com-
paring which internal units are applied in the vari-
ous gear ranges. The Clutch Application chart
provides a basis for analyzing road test results.
CLUTCH APPLICATION CHART
SLP UD OD R 2C 4C L/R OVERRUNNING
P±PARKON
R±REVERSEON ON
N-NEUTRALON
D±OVERDRIVE
FIRSTON ON* ON
SECONDON ON
SECOND PRIMEON ON
THIRDON ON
FOURTHON ON
FIFTHON ON
LIMP-INON ON
2±FIRSTON ON* ON
SECONDON ON
LIMP-INON ON
1±LOWON ON ON
*L/R clutch is on only with the output shaft speed below 150 rpm.
21 - 180 AUTOMATIC TRANSMISSION - 545RFEWJ
AUTOMATIC TRANSMISSION - 545RFE (Continued)

OPERATION
The converter impeller (Fig. 115) (driving member),
which is integral to the converter housing and bolted
to the engine drive plate, rotates at engine speed.
The converter turbine (driven member), which reacts
from fluid pressure generated by the impeller, rotates
and turns the transmission input shaft.
TURBINE
As the fluid that was put into motion by the impel-
ler blades strikes the blades of the turbine, some of
the energy and rotational force is transferred into the
turbine and the input shaft. This causes both of them
(turbine and input shaft) to rotate in a clockwise
direction following the impeller. As the fluid is leav-
ing the trailing edges of the turbine's blades it con-
tinues in a ªhinderingº direction back toward the
impeller. If the fluid is not redirected before it strikes
the impeller, it will strike the impeller in such a
direction that it would tend to slow it down.
STATOR
Torque multiplication is achieved by locking the
stator's over-running clutch to its shaft (Fig. 116).
Under stall conditions (the turbine is stationary), the
oil leaving the turbine blades strikes the face of the
stator blades and tries to rotate them in a counter-
clockwise direction. When this happens the over-run-ning clutch of the stator locks and holds the stator
from rotating. With the stator locked, the oil strikes
the stator blades and is redirected into a ªhelpingº
direction before it enters the impeller. This circula-
tion of oil from impeller to turbine, turbine to stator,
and stator to impeller, can produce a maximum
torque multiplication of about 2.4:1. As the turbine
begins to match the speed of the impeller, the fluid
that was hitting the stator in such as way as to
cause it to lock-up is no longer doing so. In this con-
dition of operation, the stator begins to free wheel
and the converter acts as a fluid coupling.
TORQUE CONVERTER CLUTCH (TCC)
In a standard torque converter, the impeller and
turbine are rotating at about the same speed and the
stator is freewheeling, providing no torque multipli-
cation. By applying the turbine's piston and friction
material to the front cover, a total converter engage-
ment can be obtained. The result of this engagement
is a direct 1:1 mechanical link between the engine
and the transmission.
The clutch can be engaged in second, third, fourth,
and fifth gear ranges depending on overdrive control
switch position. If the overdrive control switch is in
the normal ON position, the clutch will engage after
the shift to fourth gear, and above approximately 72
km/h (45 mph). If the control switch is in the OFF
Fig. 115 Torque Converter Fluid Operation - Typical
1 - APPLY PRESSURE 3 - RELEASE PRESSURE
2 - THE PISTON MOVES SLIGHTLY FORWARD 4 - THE PISTON MOVES SLIGHTLY REARWARD
21 - 268 AUTOMATIC TRANSMISSION - 545RFEWJ
TORQUE CONVERTER (Continued)

position, the clutch will engage after the shift to
third gear, at approximately 56 km/h (35 mph) at
light throttle.
The TCM controls the torque converter by way of
internal logic software. The programming of the soft-
ware provides the TCM with control over the L/R-CC
Solenoid. There are four output logic states that can
be applied as follows:
²No EMCC
²Partial EMCC
²Full EMCC
²Gradual-to-no EMCC
NO EMCC
Under No EMCC conditions, the L/R Solenoid is
OFF. There are several conditions that can result in
NO EMCC operations. No EMCC can be initiated
due to a fault in the transmission or because the
TCM does not see the need for EMCC under current
driving conditions.
PARTIAL EMCC
Partial EMCC operation modulates the L/R Sole-
noid (duty cycle) to obtain partial torque converter
clutch application. Partial EMCC operation is main-
tained until Full EMCC is called for and actuated.
During Partial EMCC some slip does occur. Partial
EMCC will usually occur at low speeds, low load and
light throttle situations.
FULL EMCC
During Full EMCC operation, the TCM increases
the L/R Solenoid duty cycle to full ON after PartialEMCC control brings the engine speed within the
desired slip range of transmission input speed rela-
tive to engine rpm.
GRADUAL-TO-NO EMCC
This operation is to soften the change from Full or
Partial EMCC to No EMCC. This is done at mid-
throttle by decreasing the L/R Solenoid duty cycle.
REMOVAL
(1) Remove transmission and torque converter
from vehicle.
(2) Place a suitable drain pan under the converter
housing end of the transmission.
CAUTION: Verify that transmission is secure on the
lifting device or work surface, the center of gravity
of the transmission will shift when the torque con-
verter is removed creating an unstable condition.
The torque converter is a heavy unit. Use caution
when separating the torque converter from the
transmission.
(3) Pull the torque converter forward until the cen-
ter hub clears the oil pump seal.
(4) Separate the torque converter from the trans-
mission.
INSTALLATION
Check converter hub and drive flats for sharp
edges, burrs, scratches, or nicks. Polish the hub and
flats with 320/400 grit paper or crocus cloth if neces-
sary. Verify that the converter hub o-ring is properly
installed and is free from debris. The hub must be
smooth to avoid damaging the pump seal at installa-
tion.
(1) Lubricate oil pump seal lip with transmission
fluid.
(2) Place torque converter in position on transmis-
sion.
CAUTION: Do not damage oil pump seal or con-
verter hub o-ring while inserting torque converter
into the front of the transmission.
(3) Align torque converter to oil pump seal open-
ing.
(4) Insert torque converter hub into oil pump.
(5) While pushing torque converter inward, rotate
converter until converter is fully seated in the oil
pump gears.
(6) Check converter seating with a scale and
straightedge (Fig. 117). Surface of converter lugs
should be at least 13 mm (1/2 in.) to rear of straight-
edge when converter is fully seated.
(7) If necessary, temporarily secure converter with
C-clamp attached to the converter housing.
Fig. 116 Stator Operation
1 - DIRECTION STATOR WILL FREE WHEEL DUE TO OIL
PUSHING ON BACKSIDE OF VANES
2 - FRONT OF ENGINE
3 - INCREASED ANGLE AS OIL STRIKES VANES
4 - DIRECTION STATOR IS LOCKED UP DUE TO OIL PUSHING
AGAINST STATOR VANES
WJAUTOMATIC TRANSMISSION - 545RFE 21 - 269
TORQUE CONVERTER (Continued)

TIRES
DESCRIPTION
DESCRIPTION - TIRES
Tires are designed and engineered for each specific
vehicle. They provide the best overall performance
for normal operation. The ride and handling charac-
teristics match the vehicle's requirements. With
proper care they will give excellent reliability, trac-
tion, skid resistance, and tread life.
Driving habits have more effect on tire life than
any other factor. Careful drivers will obtain in most
cases, much greater mileage than severe use or care-
less drivers. A few of the driving habits which will
shorten the life of any tire are:
²Rapid acceleration
²Severe brake applications
²High speed driving
²Excessive speeds on turns
²Striking curbs and other obstacles
Radial-ply tires are more prone to irregular tread
wear. It is important to follow the tire rotation inter-
val shown in the section on Tire Rotation.(Refer to 22
- TIRES/WHEELS - STANDARD PROCEDURE),
This will help to achieve a greater tread life.
TIRE IDENTIFICATION
Tire type, size, aspect ratio and speed rating are
encoded in the letters and numbers imprinted on the
side wall of the tire. Refer to the chart to decipher
the tire identification code (Fig. 12).
Performance tires have a speed rating letter after
the aspect ratio number. The speed rating is not
always printed on the tire sidewall. These ratings
are:
²Qup to 100 mph
²Sup to 112 mph
²Tup to 118 mph
²Uup to 124 mph
²Hup to 130 mph
²Vup to 149 mph
²Zmore than 149 mph (consult the tire manu-
facturer for the specific speed rating)
An All Season type tire will have eitherM+S,M
&SorM±S(indicating mud and snow traction)
imprinted on the side wall.
TIRE CHAINS
Tire snow chains may be used oncertainmodels.
Refer to the Owner's Manual for more information.
DESCRIPTION - RADIAL±PLY TIRES
Radial-ply tires improve handling, tread life and
ride quality, and decrease rolling resistance.Radial-ply tires must always be used in sets of
four. Under no circumstances should they be used on
the front only. They may be mixed with temporary
spare tires when necessary. A maximum speed of 50
MPH is recommended while a temporary spare is in
use.
Radial-ply tires have the same load-carrying capac-
ity as other types of tires of the same size. They also
use the same recommended inflation pressures.
The use of oversized tires, either in the front or
rear of the vehicle, can cause vehicle drive train fail-
ure. This could also cause inaccurate wheel speed
signals when the vehicle is equipped with Anti-Lock
Brakes.
The use of tires from different manufactures on the
same vehicle is NOT recommended. The proper tire
pressure should be maintained on all four tires.
DESCRIPTION - TIRE INFLATION PRESSURES
Under inflation will cause rapid shoulder wear, tire
flexing, and possible tire failure (Fig. 13).
Over inflation will cause rapid center wear and
loss of the tire's ability to cushion shocks (Fig. 14).
Improper inflation can cause:
²Uneven wear patterns
²Reduced tread life
²Reduced fuel economy
Fig. 12 Tire Identification
22 - 6 TIRES/WHEELSWJ

(18) Remove the four nuts that secure the steering
column to the studs on the instrument panel steering
column support bracket.
(19) Remove the steering column from the instru-
ment panel. Be certain that the steering wheel is
locked and secured from rotation to prevent the loss
of clockspring centering.
(20) Disconnect the left and right body wire har-
ness connectors, the Ignition Off Draw (IOD) wire
harness connector and the fused B(+) wire harness
connector from the connector receptacles of the JB
(Fig. 5).(21) Disconnect the instrument panel wire harness
connectors from the following floor panel transmis-
sion tunnel components (Fig. 6):
²the Airbag Control Module (ACM) connector
receptacle
²the park brake switch terminal
²the transmission shifter connector receptacle.
(22) Remove the two nuts that secure the instru-
ment panel wire harness ground eyelets to the studs
on the floor panel transmission tunnel in front of and
behind the ACM.
(23) Disengage the retainers that secure the
instrument panel wire harness to the floor panel
transmission tunnel.
(24) Remove the instrument panel to center floor
tunnel bracket from the instrument panel and the
floor panel transmission tunnel. (Refer to 23 - BODY/
INSTRUMENT PANEL/IP CENTER FLOOR TUN-
NEL BRACKET - REMOVAL).
(25) Remove the one screw that secures the floor
duct to the heater and air conditioner housing near
the driver side of the floor panel transmission tunnel
and remove the duct from the housing.
(26) If the vehicle is equipped with the manual
heating and air conditioning system, disconnect the
vacuum harness connector located near the driver
side of the floor panel transmission tunnel behind
the driver side floor duct.
(27) Remove the one screw that secures the instru-
ment panel steering column support bracket to the
driver side end of the heater and air conditioner
housing (Fig. 7).
(28) Remove the one screw that secures the instru-
ment panel steering column support bracket to the
intermediate bracket on the driver side dash panel
(Fig. 8).
Fig. 5 Junction Block Connections
1 - SNAP CLIPS
2 - SCREW
3 - CONNECTOR
4 - LEFT BODY WIRE HARNESS
5 - IOD CONNECTOR
6 - FUSED B+ CONNECTOR
7 - RIGHT BODY WIRE HARNESS
8 - SCREW
9 - CONNECTOR
10 - JUNCTION BLOCK
WJINSTRUMENT PANEL SYSTEM 23 - 39
INSTRUMENT PANEL SYSTEM (Continued)

INSTALLATION
WARNING: ON VEHICLES EQUIPPED WITH AIR-
BAGS, DISABLE THE AIRBAG SYSTEM BEFORE
ATTEMPTING ANY STEERING WHEEL, STEERING
COLUMN, OR INSTRUMENT PANEL COMPONENT
DIAGNOSIS OR SERVICE. DISCONNECT AND ISO-
LATE THE BATTERY NEGATIVE (GROUND) CABLE,
THEN WAIT TWO MINUTES FOR THE AIRBAG SYS-
TEM CAPACITOR TO DISCHARGE BEFORE PER-
FORMING FURTHER DIAGNOSIS OR SERVICE. THIS
IS THE ONLY SURE WAY TO DISABLE THE AIRBAG
SYSTEM. FAILURE TO TAKE THE PROPER PRE-
CAUTIONS COULD RESULT IN ACCIDENTAL AIR-
BAG DEPLOYMENT AND POSSIBLE PERSONAL
INJURY.
(1) Prior to installing the instrument panel into
the vehicle, loosen the three nuts that secure the
instrument panel intermediate bracket and the accel-
erator pedal assembly to the studs on the dash panel
(Fig. 8).
(2) With the aid of an assistant, load the instru-
ment panel assembly through the driver side front
door of the vehicle and hang it on the studs on the
dash panel near the windshield fence line (Fig. 1).
(3) Be certain that the molded plastic hook forma-
tions on the instrument panel structural duct are
inserted into and seated in the guide holes at each
cowl side inner panel.
(4) Loosely install the two screws that secure each
end of the instrument panel to the cowl side inner
panels.
(5) Install and tighten the two screws that secure
the passenger side instrument panel structural duct
to the heater and air conditioner housing (Fig. 13).
Tighten the screws to 11.8 N´m (105 in. lbs.).
(6) Install and tighten the one screw that secures
the instrument panel steering column support
bracket to the driver side end of the heater and air
conditioner housing (Fig. 7). Tighten the screw to
11.8 N´m (105 in. lbs.).
(7) Tighten the two screws that secure each end of
the instrument panel to the cowl side inner panels
(Fig. 10) and (Fig. 14). Tighten the screws to 11.8
N´m (105 in. lbs.).
(8) Install and tighten the one screw that secures
the instrument panel steering column support
bracket to the intermediate bracket on the driver
side dash panel (Fig. 8). Tighten the screw to 11.3
N´m (100 in. lbs.).
(9) Tighten the three nuts that secure the instru-
ment panel intermediate bracket and the accelerator
pedal assembly to the studs on the dash panel.
Tighten the nuts to 11.3 N´m (100 in. lbs.).(10) Install and tighten the four nuts that secure
the instrument panel to the studs on the dash panel
near the windshield fence line. Tighten the nuts to
11.8 N´m (105 in. lbs.).
(11) Install and tighten the nut that secures the
instrument panel steering column support bracket to
the stud on the driver side cowl plenum panel (Fig.
9). Tighten the nut to 28.2 N´m (250 in. lbs.).
(12) Reinstall the instrument panel to center floor
tunnel bracket onto the instrument panel and the
floor panel transmission tunnel. (Refer to 23 - BODY/
INSTRUMENT PANEL/IP CENTER FLOOR TUN-
NEL BRACKET - INSTALLATION).
(13) Reconnect the two instrument panel wire har-
ness connectors to the two heater and air conditioner
housing connectors located near the blower motor on
the passenger side end of the housing (Fig. 12).
(14) Reconnect the two halves of the radio antenna
coaxial cable connector near the right cowl side inner
panel under the end of the instrument panel.
(15) Reconnect the instrument panel wire harness
connector to the lower cavity of the inline connector
on the passenger side cowl side inner panel and
tighten the connector screw (Fig. 11). Tighten the
screw to 4 N´m (36 in. lbs.).
(16) Reinstall the lower right center bezel onto the
instrument panel. (Refer to 23 - BODY/INSTRU-
MENT PANEL/IP LOWER RIGHT CENTER BEZEL
- INSTALLATION).
(17) Reinstall the end cap onto the instrument
panel. (Refer to 23 - BODY/INSTRUMENT PANEL/
INSTRUMENT PANEL END CAP - INSTALLA-
TION).
(18) If the vehicle is equipped with the manual
heating and air conditioning system, reconnect the
vacuum harness connector located near the driver
side of the floor panel transmission tunnel behind
the driver side floor duct.
(19) Position the driver side floor duct to the
heater and air conditioner housing near the driver
side of the floor panel transmission tunnel (Fig. 7).
(20) Install and tighten the one screw that secures
the driver side floor duct to the heater and air con-
ditioner housing near the driver side of the floor
panel transmission tunnel. Tighten the screw to 2.2
N´m (20 in. lbs.).
(21) Route the instrument panel wire harness to
the floor panel transmission tunnel and engage the
retainers that secure the harness to the mounting
brackets on the tunnel (Fig. 6).
(22) Install the instrument panel wire harness
ground eyelets to the studs on the floor panel trans-
mission tunnel in front of and behind the airbag con-
trol module and secure the eyelets with nuts. Tighten
the nuts to 7.3 N´m (65 in. lbs.).
WJINSTRUMENT PANEL SYSTEM 23 - 43
INSTRUMENT PANEL SYSTEM (Continued)

INSTALLATION
WARNING: ON VEHICLES EQUIPPED WITH AIR-
BAGS, DISABLE THE AIRBAG SYSTEM BEFORE
ATTEMPTING ANY STEERING WHEEL, STEERING
COLUMN, OR INSTRUMENT PANEL COMPONENT
DIAGNOSIS OR SERVICE. DISCONNECT AND ISO-
LATE THE BATTERY NEGATIVE (GROUND) CABLE,
THEN WAIT TWO MINUTES FOR THE AIRBAG SYS-
TEM CAPACITOR TO DISCHARGE BEFORE PER-
FORMING FURTHER DIAGNOSIS OR SERVICE. THIS
IS THE ONLY SURE WAY TO DISABLE THE AIRBAG
SYSTEM. FAILURE TO TAKE THE PROPER PRE-
CAUTIONS COULD RESULT IN ACCIDENTAL AIR-
BAG DEPLOYMENT AND POSSIBLE PERSONAL
INJURY.
(1) If the vehicle is not equipped with the optional
automatic headlamps light sensor/vehicle theft secu-
rity system indicator, be certain that the hole plug is
installed in the clearance hole located to the out-
board side of the driver side defroster outlet in the
instrument panel top cover (Fig. 22).
(2) Before installing the top cover onto the top of
the instrument panel, be certain that the rubber top
cover seal is properly positioned on the forward edge
of the top cover panel.
(3) Position the top cover onto the top of the
instrument panel.
(4) Align the four snap clips on the top cover with
the snap clip receptacles in the instrument panel top
pad.
(5) Press firmly downward on the top cover over
each of the four snap clip locations until each of the
snap clips is fully seated in their receptacles in the
instrument panel top pad.
(6) Reconnect the battery negative cable.
INSTRUMENT PANEL TOP PAD
REMOVAL
WARNING: ON VEHICLES EQUIPPED WITH AIR-
BAGS, DISABLE THE AIRBAG SYSTEM BEFORE
ATTEMPTING ANY STEERING WHEEL, STEERING
COLUMN, OR INSTRUMENT PANEL COMPONENT
DIAGNOSIS OR SERVICE. DISCONNECT AND ISO-
LATE THE BATTERY NEGATIVE (GROUND) CABLE,
THEN WAIT TWO MINUTES FOR THE AIRBAG SYS-
TEM CAPACITOR TO DISCHARGE BEFORE PER-
FORMING FURTHER DIAGNOSIS OR SERVICE. THIS
IS THE ONLY SURE WAY TO DISABLE THE AIRBAG
SYSTEM. FAILURE TO TAKE THE PROPER PRE-
CAUTIONS COULD RESULT IN ACCIDENTAL AIR-
BAG DEPLOYMENT AND POSSIBLE PERSONAL
INJURY.(1) Disconnect and isolate the battery negative
cable.
(2) Remove the trim from the right and left A-pil-
lars. (Refer to 23 - BODY/INTERIOR/A-PILLAR
TRIM - REMOVAL).
(3) Remove the top cover from the instrument
panel. (Refer to 23 - BODY/INSTRUMENT PANEL/
INSTRUMENT PANEL TOP COVER - REMOVAL).
(4) Remove the four nuts that secure the instru-
ment panel top pad to the studs on the dash panel
near the windshield fence line (Fig. 23).
(5) Remove the speakers from the instrument
panel top pad. (Refer to 8 - ELECTRICAL/AUDIO/
SPEAKER - REMOVAL - INSTRUMENT PANEL
SPEAKER).
(6) Disengage the retainer that secures each of the
two instrument panel wire harness speaker take outs
to the mounting hole in the instrument panel top
pad. Tuck the loose ends of these speaker take outs
down the defroster ducts to keep them out of the way
during the remainder of this procedure.
(7) If the vehicle is so equipped, remove the two
screws that secure the automatic headlamp light sen-
sor/vehicle theft security system indicator unit to the
instrument panel top pad just outboard of the driver
side defroster outlet. Move the sensor/indicator unit
towards the windshield to keep it out of the way dur-
ing the remainder of this procedure.
(8) Remove the cluster bezel from the instrument
panel. (Refer to 23 - BODY/INSTRUMENT PANEL/
CLUSTER BEZEL - REMOVAL).
(9) Remove the instrument cluster from the instru-
ment panel. (Refer to 8 - ELECTRICAL/INSTRU-
MENT CLUSTER - REMOVAL).
(10) Remove the steering column opening cover
from the instrument panel. (Refer to 23 - BODY/IN-
STRUMENT PANEL/STEERING COLUMN OPEN-
ING COVER - REMOVAL).
(11) Roll the glove box down from the instrument
panel. (Refer to 23 - BODY/INSTRUMENT PANEL/
GLOVE BOX - STANDARD PROCEDURE - GLOVE
BOX ROLL DOWN).
(12) Remove the end cap from the passenger side
lower outboard end of the instrument panel. (Refer to
23 - BODY/INSTRUMENT PANEL/INSTRUMENT
PANEL END CAP - REMOVAL).
(13) Remove the lower right center bezel from the
instrument panel. (Refer to 23 - BODY/INSTRU-
MENT PANEL/IP LOWER RIGHT CENTER BEZEL
- REMOVAL).
(14) Remove the glove box lamp and switch from
the instrument panel. (Refer to 8 - ELECTRICAL/
LAMPS/LIGHTING - INTERIOR/GLOVE BOX
LAMP/SWITCH - REMOVAL).
23 - 52 INSTRUMENT PANEL SYSTEMWJ
INSTRUMENT PANEL TOP COVER (Continued)

A/C COMPRESSOR CLUTCH
DESCRIPTION
The compressor clutch assembly consists of a sta-
tionary electromagnetic coil, a hub bearing and pul-
ley assembly, and a clutch plate (Fig. 4). The
electromagnetic coil unit and the hub bearing and
pulley assembly are each retained on the nose of the
compressor front housing with snap rings. The clutch
plate is keyed to the compressor shaft and secured
with a bolt.
OPERATION
The compressor clutch components provide the
means to engage and disengage the compressor from
the engine serpentine accessory drive belt. 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 bearing, which is
part of the pulley. The compressor clutch and coil are
the only serviced parts on the compressor.
The compressor clutch engagement is controlled by
several components: the a/c switch on the a/c heater
control panel, the Automatic Zone Control (AZC) con-
trol module (if the vehicle is so equipped), the evap-
orator probe, the a/c high pressure transducer, the
a/c compressor clutch relay, the body control module
(BCM) and the Powertrain Control Module (PCM).
The PCM may delay compressor clutch engagement
for up to thirty seconds. Refer to Electronic Control
Modules for more information on the PCM controls.
DIAGNOSIS AND TESTING - COMPRESSOR
CLUTCH COIL
For circuit descriptions and diagrams, refer to the
appropriate wiring diagrams. The battery must be
fully-charged before performing the following tests.
Refer to Battery for more information.
(1) Connect an ammeter (0 to 10 ampere scale) in
series with the clutch coil terminal. Use a voltmeter
(0 to 20 volt scale) with clip-type leads for measuring
the voltage across the battery and the compressor
clutch coil.
(2) With the a/c heater mode control switch in any
a/c mode, the a/c heater control a/c switch in the ON
position, and the blower motor switch in the lowest
speed position, start the engine and run it at normal
idle.
(3) The compressor clutch coil voltage should read
within 0.2 volts of the battery voltage. If there is
voltage at the clutch coil, but the reading is not
within 0.2 volts of the battery voltage, test the clutch
coil feed circuit for excessive voltage drop and repair
as required. If there is no voltage reading at the
clutch coil, use a DRBIIItscan tool and the appro-
priate diagnostic information for testing of the com-
pressor clutch circuit. The following components
must be checked and repaired as required before you
can complete testing of the clutch coil:
²Fuses in the junction block and the Power Dis-
tribution Center (PDC)
²A/C heater mode control switch
²A/C compressor clutch relay
²A/C high pressure transducer
²A/C evaporator probe
²Powertrain Control Module (PCM)
²Body Control Module (BCM)
(4) The compressor clutch coil is acceptable if the
current draw measured at the clutch coil is 2.0 to 3.9
amperes with the electrical system voltage at 11.5 to
12.5 volts. This should only be checked with the work
area temperature at 21É C (70É F). If system voltage
is more than 12.5 volts, add electrical loads by turn-
ing on electrical accessories until the system voltage
drops below 12.5 volts.
(a) If the clutch coil current reading is four
amperes or more, the coil is shorted and should be
replaced.
(b) If the clutch coil current reading is zero, the
coil is open and should be replaced.
Fig. 4 COMPRESSOR CLUTCH - TYPICAL
1 - CLUTCH PLATE
2 - SHAFT KEY
3 - PULLEY
4 - COIL
5 - CLUTCH SHIMS
6 - SNAP RING
7 - SNAP RING
WJCONTROLS 24 - 13