2003 JEEP GRAND CHEROKEE stall

(7) Remove the external snap ring that secures the
compressor clutch coil to the nose of the compressor
front housing with snap ring pliers and slide the coil
assembly off of the compressor (Fig. 8).
INSPECTION
Examine the friction surfaces of the clutch pulley
and the clutch plate for wear. The pulley and plate
should be replaced if there is excessive wear or scor-
ing.
If the friction surfaces are oily, inspect the shaft
and nose area of the compressor for refrigerant oil.
Remove the felt wick from around the shaft inside
the nose of the compressor front housing. If the felt
is saturated with refrigerant oil, the compressor
shaft seal is leaking and the compressor must be
replaced.
Check the clutch pulley bearing for roughness or
excessive leakage of grease. Replace the bearing, if
required.
INSTALLATION
(1) Align the dowel pin on the back of the clutch
field coil with the hole in the compressor front hous-
ing and press the field coil into place over the nose of
the compressor.
(2) Install the clutch coil lead wire harness retain-
ing clip on the compressor front housing and tighten
the retaining screw.(3) Install the clutch field coil and snap ring with
snap ring pliers (Special Tool C-4574). The bevel side
of the snap ring must be facing outward. Also, both
eyelets of the snap ring must be to the right or left of
the pin on the compressor. Press in on the snap ring
to be certain that it is properly seated in the groove.
CAUTION: If the snap ring is not fully seated in the
groove it will vibrate out, resulting in a clutch fail-
ure and severe damage to the front housing of the
compressor.
(4) Install the pulley assembly onto the compres-
sor. If necessary, place a block of wood on the friction
surface and tap gently with a hammer (Fig. 9).
CAUTION: Do not mar the pulley friction surface.
(5) Install the pulley assembly retaining snap ring
(bevel side outward) with snap ring pliers (Special
Tool C-4574). Press in on the snap ring to be certain
that it is properly seated in the groove.
(6) If the original clutch plate assembly and pulley
assembly are to be reused, the old shim(s) can be
used. If not, place a stack of shim(s) equal to the old
shim(s) on the shaft against the shoulder.
(7) Install the clutch plate assembly onto the
shaft.
(8) With the clutch plate assembly tight against
the shim(s), measure the air gap between the clutch
plate and the pulley face with feeler gauges. The air
Fig. 8 CLUTCH COIL SNAP RING
1 - SNAP RING PLIERS
2 - CLUTCH COIL
3 - SNAP RING
4 - COMPRESSOR
Fig. 9 PULLEY ASSEMBLY INSTALL
1 - PULLEY ASSEMBLY
2 - WOOD BLOCK
WJCONTROLS 24 - 15
A/C COMPRESSOR CLUTCH (Continued)

gap should be between 0.35 to 0.65 millimeter (0.014
to 0.026 inch). If the proper air gap is not obtained,
add or subtract shims as needed until the desired air
gap is obtained.
(9) Install the compressor shaft bolt. Tighten the
bolt to 13 N´m (115 in. lbs.).
NOTE: The shims may compress after tightening
the shaft bolt. Check the air gap in four or more
places to verify the air gap is still correct. Spin the
pulley before performing a final check of the air
gap.
(10) To complete the installation, (Refer to 24 -
HEATING & AIR CONDITIONING/PLUMBING/A/C
COMPRESSOR - INSTALLATION)
A/C COMPRESSOR CLUTCH
RELAY
DESCRIPTION
The compressor clutch relay is a International
Standards Organization (ISO) micro-relay. The termi-
nal designations and functions are the same as a con-
ventional ISO relay. However, the micro-relay
terminal orientation (footprint) is different, the cur-
rent capacity is lower, and the relay case dimensions
are smaller than those of the conventional ISO relay.
OPERATION
The compressor clutch relay is a electromechanical
device that switches battery current to the compres-
sor clutch coil when the Powertrain Control Module
(PCM) grounds the coil side of the relay. The PCM
responds to inputs from the a/c compressor switch on
the a/c heater control panel, the Automatic Zone Con-
trol (AZC) control module (if the vehicle is so
equipped), the a/c fin probe, and the a/c high pres-
sure transducer. (Refer to 24 - HEATING & AIR
CONDITIONING/CONTROLS/A/C COMPRESSOR
CLUTCH RELAY - DIAGNOSIS AND TESTING)
The compressor clutch relay is located in the Power
Distribution Center (PDC) in the engine compart-
ment. Refer to the PDC label for relay identification
and location.
The compressor clutch relay cannot be repaired
and, if faulty or damaged, it must be replaced.
DIAGNOSIS AND TESTING - A/C COMPRESSOR
CLUTCH RELAY
For circuit descriptions and diagrams, refer to the
appropriate wiring information.
The compressor clutch relay (Fig. 10) is located in
the Power Distribution Center (PDC). Refer to the
PDC label for relay identification and location.Remove the relay from the PDC to perform the fol-
lowing tests:
(1) A relay in the de-energized position should
have continuity between terminals 87A and 30, and
no continuity between terminals 87 and 30. If OK, go
to Step 2. If not OK, replace the faulty relay.
(2) Resistance between terminals 85 and 86 (elec-
tromagnet) should be 75   5 ohms. If OK, go to Step
3. If not OK, replace the faulty relay.
(3) Connect a battery to terminals 85 and 86.
There should now be continuity between terminals
30 and 87, and no continuity between terminals 87A
and 30. If OK, see the Relay Circuit Test procedure
in this group. If not OK, replace the faulty relay.
RELAY CIRCUIT TEST
For circuit descriptions and diagrams, refer to the
appropriate wiring information..
(1) The relay common feed terminal cavity (30) is
connected to fused battery feed. There should be bat-
tery voltage at the cavity for relay terminal 30 at all
times. If OK, go to Step 2. If not OK, repair the open
circuit to the fuse in the PDC as required.
(2) The relay normally closed terminal (87A) is not
used in this application. Go to Step 3.
(3) The relay normally open terminal cavity (87) is
connected to the compressor clutch coil. There should
be continuity between this cavity and the A/C com-
pressor clutch relay output circuit cavity of the com-
pressor clutch coil wire harness connector. If OK, go
to Step 4. If not OK, repair the open circuit as
required.
(4) The relay coil battery terminal (86) is con-
nected to the fused ignition switch output (run/start)
circuit. There should be battery voltage at the cavity
for relay terminal 86 with the ignition switch in the
On position. If OK, go to Step 5. If not OK, repair the
Fig. 10 A/C COMPRESSOR CLUTCH RELAY
30 - COMMON FEED
85 - COIL GROUND
86 - COIL BATTERY
87 - NORMALLY OPEN
87A - NORMALLY CLOSED
24 - 16 CONTROLSWJ
A/C COMPRESSOR CLUTCH (Continued)

open circuit to the fuse in the junction block as
required.
(5) The coil ground terminal cavity (85) is switched
to ground through the Powertrain Control Module
(PCM). There should be continuity between this cav-
ity and the A/C compressor clutch relay control cir-
cuit cavity of the PCM wire harness connector C
(gray) at all times. If not OK, repair the open circuit
as required.
REMOVAL
(1) Disconnect and isolate the battery negative
cable.
(2) Remove the cover from the Power Distribution
Center (PDC) (Fig. 11).
(3) Refer to the label on the PDC for compressor
clutch relay identification and location.
(4) Unplug the compressor clutch relay from the
PDC.
INSTALLATION
(1) Install the compressor clutch relay by aligning
the relay terminals with the cavities in the PDC and
pushing the relay firmly into place.
(2) Install the PDC cover.
(3) Connect the battery negative cable.
(4) Test the relay operation.
A/C HEATER CONTROL
DESCRIPTION
The manual temperature control HVAC system
uses a combination of electrical, and vacuum con-trols. The Automatic Zone Control (AZC) HVAC sys-
tem uses only electrical controls. These controls
provide the vehicle operator with a number of setting
options to help control the climate and comfort
within the vehicle. Refer to the owner's manual in
the vehicle glove box for more information on the
suggested operation and use of these controls.
Both a/c heater control panels are located on the
instrument panel inboard of the steering column and
below the radio (Fig. 12). Both control panels contain
rotary-type temperature control knob(s), a rotary-
type mode control switch knob, a rotary-type blower
motor speed switch knob and an air conditioning
compressor push button switch. The rear window
defogger push button switch is also located on a/c
heater control panel. The AZC control panel also fea-
tures a recirculation push button switch and a vac-
uum fluorescent display area.
OPERATION
The AZC control module uses infrared sensing
technology to control occupant comfort levels, not the
actual passenger compartment air temperature. Dual
infrared sensors mounted in the face of the control
unit independently measure the surface temperature
to maintain customer-perceived comfort temperature
under changing conditions. Dual Zone temperature
control provides wide side-to-side variation in comfort
temperature to exceed the needs of either front seat
occupant. This sensing system replaces interior air
temperature and solar sensors used to approximate
direct sensing control through complex control pro-
grams.
Fig. 11 POWER DISTRIBUTION CENTER (PDC)
1 - TRANSMISSION CONTROL MODULE (TCM)
2 - NEGATIVE CABLE
3 - POSITIVE CABLE
4 - POWER DISTRIBUTION CENTER (PDC)
Fig. 12 A/C HEATER CONTROL PANELS
WJCONTROLS 24 - 17
A/C COMPRESSOR CLUTCH RELAY (Continued)

HVAC SYSTEM POINTER
While the value of this pointer
is being displayed, turning the
right set temperature control
either direction will manually
control the value. CW =
increase; CCW = decrease
05 Avg NPRG 0 TO
255
While the value of this pointer
is being displayed, turning the
right set temperature control
either direction will manually
control the value. CW =
increase; CCW = decrease
06 Primary control side 0 or 1
0 = left 1
= right
07 EE Check sum (calculated) 0 to 255
08 Target intensity (in % ON time) 0 to 255
While the value of this pointer
is being displayed, turning the
right set temperature control
either direction will manually
control the value. CW =
increase; CCW = decrease
09 Not Used 0 to 0
10 Not Used 0 to 0
11 Right NINC * 0 to 255
* NINC equals a calculated number based on the IR
sensor and IR thermistor values used to calculate the
NPRG.
While the value of this pointer
is being displayed, turning the
right set temperature control
either direction will manually
control the value. CW =
increase; CCW = decrease
12 Left NINC 0 to 255
While the value of this pointer
is being displayed, turning the
right set temperature control
either direction will manually
control the value. CW =
increase; CCW = decrease
13 Right NMIX * 0 to 255
* NMIX equals a calculated number based on outside
and in-vehicle conditions used by the AZC to position
the Temperature motors.HVAC SYSTEM POINTER
While the value of this pointer
is being displayed, turning the
right set temperature control
either direction will manually
control the value. CW =
increase; CCW = decrease
14 Left NMIX 0 to 255
While the value of this pointer
is being displayed, turning the
right set temperature control
either direction will manually
control the value. CW =
increase; CW = decrease
15 Not Used 0 to 0
16 Not Used 0 to 0
17 Reserved
18 Reserved
19 Reserved
MODE VALUE POINTER
Pointer
NumberDESCRIPTION Value
Displayed
20 mode range in delta counts 0 to
9999
21 Current mode position (in
counts)0to
9999
22 mode target position in ratio 0 to 255
While the value of this pointer
is being displayed, turning the
right set temperature control
either direction will manually
control the value. CW =
increase; CCW = decrease
23 mode target position in counts 0 to
9999
24 Not Used 0 to 0
25 number of valve moves since
last index0to
9999
26 Not Used 0 to 0
27 Not Used 0 to 0
28 Not Used 0 to 0
29 mode motor state 0 to 5
0 = in position, 1 = moving
toward panel, 2 = moving
toward defrost, 3 = searching
range, 4 = stalled moving
toward panel, 5 = stalled
moving toward defrost
24 - 22 CONTROLSWJ
A/C HEATER CONTROL (Continued)

LEFT SIDE TEMPERATURE POINTER
Pointer
NumberDESCRIPTION Value
Displayed
30 Left side temp range in delta
counts0to
9999
31 Current left side temp position
(in counts)0to
9999
32 Left side temp target position
(in ratio)0to255
While the value of this pointer
is being displayed, turning the
right set temperature control
either direction will manually
control the value. CW =
increase; CCW = decrease
33 Left side temp target in counts 0 to
9999
34 Not used 0 to 0
35 number of valve moves since
last index0to
9999
36 Not used 0 to 0
37 Not used 0 to 0
38 Not used 0 to 0
39 Left side temp motor state 0 to 5
0 = in position, 1 = moving
toward panel, 2 = moving
toward defrost, 3 = searching
range, 4 = stalled moving
toward panel, 5 = stalled
moving toward defrost
RIGHT SIDE TEMPERATURE POINTER
Pointer
NumberDESCRIPTION Value
Displayed
40 Right side temp range in delta
counts0to
9999
41 Current right side temp
position (in counts)0to
9999
42 Right side temp target position
(in ratio)0to255
While the value of this pointer
is being displayed, turning the
right set temperature control
either direction will manually
control the value. CW =
increase; CCW = decrease
43 Right side temp target in
counts0to
9999
44 Not used 0 to 0
RIGHT SIDE TEMPERATURE POINTER
45 number of valve moves since
last index0to
9999
46 Not used 0 to 0
47 Not used 0 to 0
48 Not used 0 to 0
49 Right side temp motor state 0 to 5
0 = in position, 1 = moving
toward panel, 2 = moving
toward defrost, 3 = searching
range, 4 = stalled moving
toward panel, 5 = stalled
moving toward defrost
AIR INLET POINTER
Pointer
NumberDESCRIPTION Value
Displayed
50 Air inlet range (in counts) 0 to
9999
51 Current air inlet position (in
counts)0to
9999
52 Air inlet target position (in
ratio)0to255
While the value of this pointer
is being displayed, turning the
right set temperature control
either direction will manually
control the value. CW =
increase; CCW = decrease
53 Air inlet target in counts 0 to
9999
54 Not used 0 to 0
55 number of motor moves since
last index0to
9999
56 Not used 0 to 0
57 Not used 0 to 0
58 Not used 0 to 0
59 Air inlet motor state 0 to 5
0 = in position, 1 = moving
toward panel, 2 = moving
toward defrost, 3 = searching
range, 4 = stalled moving
toward panel, 5 = stalled
moving toward defrost
60 Reserved
61 Actual Outside Air Temp (in
degrees F)-40 to
215
62 Not used 0 to 0
WJCONTROLS 24 - 23
A/C HEATER CONTROL (Continued)

INSTALLATION
(1) Plug the wire harness and/or vacuum harness
connectors into the back of the a/c heater control.
(2) Position the a/c heater control in the instru-
ment panel and secure it with 4 screws. Tighten the
screws to 2.2 N´m (20 in. lbs.).
(3) Reinstall the center upper, and center lower
bezels onto the instrument panel. Refer to Instru-
ment Panel System for the procedures.
(4) Connect the battery negative cable.
A/C PRESSURE TRANSDUCER
DESCRIPTION
The A/C pressure transducer is installed on a fit-
ting located on the refrigerant discharge line near
the condenser. An internally threaded hex fitting on
the transducer connects it to the externally threaded
Schrader-type fitting on the discharge line. A rubber
O-ring seals the connection between the transducer
and the discharge line fitting. Three terminals within
a molded plastic connector receptacle on the top of
the transducer connect it to the vehicle electrical sys-
tem through a take out and connector of the head-
lamp and dash wire harness.
The A/C pressure transducer cannot be adjusted or
repaired and if faulty or damaged, it must be
replaced.
OPERATION
The A/C pressure transducer monitors the pres-
sures in the high side of the refrigerant system
through its connection to a fitting on the discharge
line. The transducer will change its internal resis-
tance in response to the pressures it monitors. The
Powertrain Control Module (PCM) provides a five
volt reference signal and a sensor ground to the
transducer, then monitors the output voltage of the
transducer on a sensor return circuit to determine
refrigerant pressure. The PCM is preporgrammed to
respond to this and other sensor inputs by controlling
the operation of the air conditioning compressor
clutch and the radiator cooling fan to help optimize
air conditioning system performance and to protect
the system components from damage. The A/C pres-
sure transducer input to the PCM will also prevent
the air conditioning compressor clutch from engaging
when the ambient temperatures are below about
0.556É C (33É F) due to the pressure/temperature
relationship of the refrigerant. The Schrader-type
valve in the liquid line fitting permits the A/C pres-
sure transducer to be removed or installed without
distrubing the refrigerant in the system. The A/C
pressure transducer is diagnosed using the DRBIIIt
scan tool. Refer to the appropriate diagnostic infor-
mation.
Fig. 13 A/C HEATER CONTROL REMOVE/INSTALL
1 - MOUNTING SCREW TABS
Fig. 14 A/C HEATER CONTROL CONNECTIONS
1 - MODE SWITCH
2 - ELECTRICAL CONNECTIONS
3 - VACUUM HARNESS
WJCONTROLS 24 - 25
A/C HEATER CONTROL (Continued)

DIAGNOSIS AND TESTING - A/C PRESSURE
TRANSDUCER
The A/C pressure transducer is tested using a
DRBIIItscan tool. Refer to the appropriate diagnos-
tic information. Before testing the A/C pressure
transducer, be certain that the transducer wire har-
ness connection is clean of corrosion and properly
connected. For the air conditioning system to operate,
an A/C pressure transducer voltage reading between0.7 and 4.56 volts is required. Voltage outside this
range indicate a low or high refrigerant system pres-
sure condition to the Powertrain Control Module
(PCM). The PCM is programmed to respond to a low
or high refrigerant system pressure by suppressing
operation of the compressor. Refer to the A/C Pres-
sure Transducer Voltage table for the possible condi-
tion indicated by the transducer voltage readings.
A/C PRESSURE TRANSDUCER VOLTAGE
VOLTAGE POSSIBLE INDICATION
0.0 1. NO SENSOR SUPPLY VOLTAGE FROM PCM.
2. SHORTED SENSOR CIRCUIT.
3. FAULTY TRANSDUCER
0.150 TO 0.450 1. AMBIENT TEMPERATURE BELOW 10É c (50É F).
2. LOW REFRIGERANT SYSTEM PRESSURE.
0.451 TO 4.519 1. NORMAL REFRIGERANT SYSTEM PRESSURE.
4.520 TO 4.850 1. HIGH REFRIGERANT SYSTEM PRESSURE.
5.0 1. OPEN SENSOR CIRCUIT.
2. FAULTY TRANSDUCER.
REMOVAL
WARNING: Transducer can be removed without
recoverying the system, but some loss of refriger-
ant can be expected(Refer to 24 - HEATING & AIR
CONDITIONING/PLUMBING - WARNING) and (Refer
to 24 - HEATING & AIR CONDITIONING/PLUMBING -
CAUTION).
(1) Disconnect and isolate the battery negative
cable.
(2) Disconnect the headlamp and dash wire har-
ness connector for the A/C pressure transducer from
the transducer connector receptacle.
(3) Using an open end wrench, unscrew the A/C
pressure transducer from the fitting on the discharge
line.
(4) Remove the seal from the A/C pressure trans-
ducer fitting and discard.
INSTALLATION
(1) Lubricate a new O-ring seal with clean refrig-
erant oil and install it on the A/C pressure trans-
ducer fitting.
(2) Using an open end wrench, install and tighten
the A/C pressure transducer onto the fitting on the
discharge line.
(3) Reconnect the headlamp and dash wire harness
connector for the A/C pressure transducer to the
transducer connector receptacle.(4) Reconnect the battery negative cable.
BLOWER MOTOR
CONTROLLER
DESCRIPTION
Models equipped with the optional Automatic Zone
Control (AZC) system have a blower motor controller.
The controller allows the selection of almost infi-
nitely variable blower motor speeds. The controller is
mounted to the HVAC housing, under the instrument
panel and just inboard of the blower motor, in the
same location used for the blower motor resistor on
manual temperature control systems. It can be
accessed without removing any other components.
OPERATION
The blower motor controller output to the blower
motor can be adjusted by the blower motor speed
switch knob on the AZC A/C Heater control panel, or
it can be adjusted automatically by the logic circuitry
and programming of the AZC control module. In
either case, the AZC control module sends the correct
pulse width modulated signal to the blower motor
controller to obtain the selected or programmed
blower motor speed.
The blower motor controller cannot be repaired
and, if faulty or damaged, it must be replaced.
24 - 26 CONTROLSWJ
A/C PRESSURE TRANSDUCER (Continued)

REMOVAL
(1) Disconnect and isolate the battery negative
cable.
(2) Depress locking tab and unplug the wire har-
ness connector from the blower motor controller.
(3) Depress locking tab and unplug the controller
connector from the blower motor.
(4) Remove the 2 screws that secure the blower
motor controller to the HVAC housing.
(5) Remove the blower motor controller from the
HVAC housing (Fig. 15).
INSTALLATION
(1) Install the blower motor controller in the
HVAC housing. The housing is indexed to allow con-
troller mounting in only one position. Tighten the
mounting screws to 2.2 N´m (20 in. lbs.).
(2) Plug in the wire harness connector to the
blower motor controller.
(3) Plug in the connector from the blower motor
controller to the blower motor.
(4) Connect the battery negative cable.
BLOWER MOTOR RESISTOR
BLOCK
DESCRIPTION
Models with the standard manual temperature
control system have a blower motor resistor. The
blower motor resistor is mounted to the bottom of the
HVAC housing, under the instrument panel and just
inboard of the blower motor. It can be accessed for
service without removing any other components.
OPERATION
The resistor has multiple resistor wires, each of
which will reduce the current flow to the blower
motor to change the blower motor speed by changing
the resistance in the blower motor ground path. The
blower motor switch directs the ground path through
the correct resistor wire to obtain the selected speed.
With the blower motor switch in the lowest speed
position, the ground path for the motor is applied
through all of the resistor wires. Each higher speed
selected with the blower motor switch applies the
blower motor ground path through fewer of the resis-
tor wires, increasing the blower motor speed. When
the blower motor switch is in the highest speed posi-
tion, the blower motor resistor is bypassed and the
blower motor receives a direct path to ground.
The blower motor resistor cannot be repaired and,
if faulty or damaged, it must be replaced.
DIAGNOSIS AND TESTING - BLOWER MOTOR
RESISTOR BLOCK
For circuit descriptions and diagrams, refer to the
appropriate wiring information.
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 AN ACCIDENTAL
AIRBAG DEPLOYMENT AND POSSIBLE PERSONAL
INJURY.
(1) Disconnect and isolate the battery negative
cable.
(2) Unplug the wire harness connector from the
blower motor resistor.
Fig. 15 BLOWER MOTOR CONTROLLER REMOVE/
INSTALL
1 - BLOWER MOTOR CONTROLLER
2 - BLOWER MOTOR
3 - GROUND STRAP
4 - ELECTRICAL CONNECTORS
5 - HEATER CORE TUBES
WJCONTROLS 24 - 27
BLOWER MOTOR CONTROLLER (Continued)