2003 JEEP GRAND CHEROKEE diagram

(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.
(6) Solder the connection together using rosin core
type solder only.Do not use acid core solder.
(7) Tape the diode to the harness using electrical
tape making, sure the diode is completely sealed
from the elements.
(8) Re-connect the battery, and test affected sys-
tems.SPECIFICATIONS
A/C APPLICATION TABLE
Item Description Notes
VEHICLE WJ - Grand
Cherokee
SYSTEM R134a w/
expansion valve
COMPRESSOR Nippondenso
10PA17ND-8 PAG oil
Freeze±up
ControlEvaporator Probe Evaporator
mounted
Low psi Control opens < 22 psi -
resets > 34-38 psi
High psi Control opens > 450-490
psi - resets <
270-330 psiline mounted
CONTROL
HEADManual type manual
controls
Automatic Zone
Control (AZC)Automatic
Zone Control
(AZC) with
dual infrared
sensing
Mode Doors Vacuum actuators
(manual)electric
actuator
(AZC)
Blend Door Electric actuator (manual and
AZC)
Blend Door
(passenger)Electric actuator (AZC only)
Recirculation
DoorVacuum actuator
(manual)electric
actuator
(AZC)
Blower Motor Hardwired to
control head
resistor block
(manual),
blower
controller (AZC)
COOLING FAN Hybrid - viscous
clutch/electricPCM output
CLUTCH
Control Relay PCM
controlled
Draw
2.0-3.9 amps @ 12 V  0.5V@ 70É F
Gap 0.0169-0.0319
DRB IIIT
Reads TPS, RPM, A/C
switch
Actuators Clutch relay
WJHEATING & AIR CONDITIONING 24 - 7
HEATING & AIR CONDITIONING (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

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)

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)

(3) Check for continuity between each of the
blower motor switch input terminals of the resistor
and the resistor output terminal. In each case there
should be continuity. If OK, repair the wire harness
circuits between the blower motor switch and the
blower motor resistor or blower motor as required. If
not OK, replace the faulty blower motor resistor.
REMOVAL
(1) Disconnect and isolate the battery negative
cable.
(2) Depress locking tab and unplug the wire har-
ness connector from the blower motor resistor.
(3) Depress locking tab and unplug the resistor
connector from the blower motor.
(4) Remove the 2 screws that secure the blower
motor resistor to the HVAC housing.
(5) Remove the blower motor resistor from the
HVAC housing (Fig. 16).
INSTALLATION
(1) Install the blower motor resistor in the HVAC
housing. The housing is indexed to allow 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 resistor.(3) Plug in the connector from the blower motor
resistor to the blower motor.
(4) Connect the battery negative cable.
BLOWER MOTOR SWITCH
DESCRIPTION
The A/C Heater blower motor is controlled by a
rotary-type blower motor switch, mounted in the A/C
Heater control panel. On vehicles with manual tem-
perature control systems, the switch allows the selec-
tion of four blower motor speeds, but will only
operate with the ignition switch in the On position
and the A/C Heater mode control switch in any posi-
tion, except Off. On vehicles with the Automatic Zone
Control (AZC) systems, the switch allows the selec-
tion of Lo Auto, Hi Auto, and ten speed settings
between Lo and Hi.
OPERATION
On manual temperature control systems, the
blower motor switch is connected in series with the
blower motor ground path through the a/c heater
mode control switch. The blower motor switch directs
this ground path to the blower motor through the
blower motor resistor wires, or directly to the blower
motor, as required to achieve the selected blower
motor speed.
On AZC systems, the blower motor switch is just
one of many inputs to the AZC control module. In the
manual blower modes, the AZC control module
adjusts the blower motor speed through the blower
motor controller as required to achieve the selected
blower switch position. In the auto blower modes, the
AZC control assembly is programmed to select and
adjust the blower motor speed through the blower
motor controller as required to achieve and maintain
the selected comfort level.
The blower motor switch cannot be repaired and, if
faulty or damaged, it must be replaced. The switch is
serviced only as a part of the a/c heater control
assembly.
DIAGNOSIS AND TESTING - BLOWER MOTOR
SWITCH-MANUAL TEMPERATURE CONTROL
SYSTEM
For circuit descriptions and diagrams, refer to the
appropriate wiring information.
Fig. 16 BLOWER MOTOR RESISTOR REMOVE/
INSTALL
1 - BLOWER MOTOR RESISTOR
2 - BLOWER MOTOR
3 - GROUND STRAP
4 - ELECTRICAL CONNECTORS
5 - HEATER CORE TUBES
24 - 28 CONTROLSWJ
BLOWER MOTOR RESISTOR BLOCK (Continued)

BLOWER MOTOR
DESCRIPTION
The blower motor and blower wheel are located in
the passenger side end of the HVAC housing, below
the glove box module. The blower motor controls the
velocity of the air flowing through the HVAC housing
by spinning a squirrel cage-type blower wheel within
the housing at the selected speed. The blower motor
and blower wheel can be serviced from the passenger
compartment side of the housing.
OPERATION
The blower motor will only operate when the igni-
tion switch is in the On position, and the a/c heater
mode control switch is in any position, except off. The
blower motor circuit is protected by a fuse in the
junction block. On models with the standard manual
temperature control system, the blower motor speed
is controlled by regulating the battery feed through
the blower motor switch and the blower motor resis-
tor. On models with the optional Automatic Zone
Control (AZC) system, the blower motor speed is con-
trolled by using Pulse Width Modulation (PWM). The
blower motor controller adjusts the battery feed volt-
age to the blower motor, based upon an input from
the blower motor switch, through the AZC control
module. Pulse width modulation of blower power
allows the blower to operate at any speed from sta-
tionary, to full speed.
The blower motor and blower motor wheel cannot
be repaired, and if faulty or damaged, they must be
replaced. The blower motor and blower wheel are
each serviced separately.
DIAGNOSIS AND TESTING - BLOWER MOTOR
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.
For circuit descriptions and diagrams, refer to the
appropriate wiring information. Possible causes of an
inoperative blower motor include:
²Faulty fuse²Faulty blower motor circuit wiring or wire har-
ness connections
²Faulty blower motor resistor (if the vehicle is so
equipped)
²Faulty blower motor controller (if the vehicle is
so equipped)
²Faulty blower motor switch
²Faulty a/c heater mode control switch
²Faulty blower motor.
Possible causes of the blower motor not operating
in all speeds include:
²Faulty fuse
²Faulty blower motor switch
²Faulty blower motor resistor (if the vehicle is so
equipped)
²Faulty blower motor controller (if the vehicle is
so equipped)
²Faulty AZC module (if the vehicle is so
equipped)
²Faulty blower motor circuit wiring or wire har-
ness connections.
VIBRATION
Possible causes of blower motor vibration include:
²Improper blower motor mounting
²Improper blower wheel mounting
²Blower wheel out of balance or bent
²Blower motor faulty.
NOISE
To verify that the blower is the source of the noise,
unplug the blower motor wire harness connector and
operate the HVAC system. If the noise goes away,
possible causes include:
²Foreign material in the HVAC housing
²Improper blower motor mounting
²Improper blower wheel mounting
²Blower motor faulty.
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 AN ACCIDENTAL
AIRBAG DEPLOYMENT AND POSSIBLE PERSONAL
INJURY.
WJDISTRIBUTION 24 - 37