1995 JEEP XJ heater

²The powertrain control module (PCM) pre-posi-
tions the idle air control (IAC) motor.
²The PCM determines atmospheric air pressure
from the MAP sensor input to determine basic fuel
strategy.
²The PCM monitors the engine coolant temperature
sensor input. The PCM modifies fuel strategy based
on this input.
²Intake manifold air temperature sensor input is
monitored
²Throttle position sensor (TPS) is monitored
²The auto shutdown (ASD) relay is energized by the
PCM for approximately three seconds.
²The fuel pump is energized through the fuel pump
relay by the PCM. The fuel pump will operate for ap-
proximately three seconds unless the engine is oper-
ating or the starter motor is engaged
²The O2S sensor heater element is energized
through the fuel pump relay. The O2S sensor input is
not used by the PCM to calibrate air-fuel ratio dur-
ing this mode of operation.
²The up-shift indicator lamp is illuminated (manual
transmission only).
ENGINE START-UP MODE
This is an Open Loop mode. The following actions
occur when the starter motor is engaged.
The powertrain control module (PCM) receives in-
puts from:
²Battery voltage
²Engine coolant temperature sensor
²Crankshaft position sensor
²Intake manifold air temperature sensor
²Manifold absolute pressure (MAP) sensor
²Throttle position sensor (TPS)
²Starter motor relay
²Camshaft position sensor signal
The PCM monitors the crankshaft position sensor.
If the PCM does not receive a crankshaft position
sensor signal within 3 seconds of cranking the en-
gine, it will shut down the fuel injection system.
The fuel pump is activated by the PCM through
the fuel pump relay.
Voltage is applied to the fuel injectors with the
PCM. The PCM will then control the injection se-
quence and injector pulse width by turning the
ground circuit to each individual injector on and off.
The PCM determines the proper ignition timing ac-
cording to input received from the crankshaft posi-
tion sensor.
ENGINE WARM-UP MODE
This is an Open Loop mode. During engine warm-
up, the powertrain control module (PCM) receives in-
puts from:
²Battery voltage
²Crankshaft position sensor
²Engine coolant temperature sensor²Intake manifold air temperature sensor
²Manifold absolute pressure (MAP) sensor
²Throttle position sensor (TPS)
²Camshaft position sensor signal (in the distribu-
tor)
²Park/neutral switch (gear indicator signalÐauto.
trans. only)
²Air conditioning select signal (if equipped)
²Air conditioning request signal (if equipped)
Based on these inputs the following occurs:
²Voltage is applied to the fuel injectors with the
powertrain control module (PCM). The PCM will
then control the injection sequence and injector pulse
width by turning the ground circuit to each individ-
ual injector on and off.
²The PCM adjusts engine idle speed through the
idle air control (IAC) motor and adjusts ignition tim-
ing.
²The PCM operates the A/C compressor clutch
through the clutch relay. This is done if A/C has been
selected by the vehicle operator and requested by the
A/C thermostat.
²If the vehicle has a manual transmission, the up-
shift lamp is operated by the PCM.
²When engine has reached operating temperature,
the PCM will begin monitoring O2S sensor input.
The system will then leave the warm-up mode and go
into closed loop operation.
IDLE MODE
When the engine is at operating temperature, this
is a Closed Loop mode. At idle speed, the powertrain
control module (PCM) receives inputs from:
²Air conditioning select signal (if equipped)
²Air conditioning request signal (if equipped)
²Battery voltage
²Crankshaft position sensor
²Engine coolant temperature sensor
²Intake manifold air temperature sensor
²Manifold absolute pressure (MAP) sensor
²Throttle position sensor (TPS)
²Camshaft position sensor signal (in the distribu-
tor)
²Battery voltage
²Park/neutral switch (gear indicator signalÐauto.
trans. only)
²Oxygen sensor
Based on these inputs, the following occurs:
²Voltage is applied to the fuel injectors with the
powertrain control module (PCM). The PCM will
then control injection sequence and injector pulse
width by turning the ground circuit to each individ-
ual injector on and off.
²The PCM monitors the O2S sensor input and ad-
justs air-fuel ratio by varying injector pulse width. It
also adjusts engine idle speed through the idle air
control (IAC) motor.
JFUEL SYSTEM COMPONENT DESCRIPTION/SYSTEM OPERATION 14 - 31

(4) Remove the cover retaining screws and remove
the cover from the console (Fig. 7).
(5) Remove the remainder of the console attaching
screws from the brackets and disconnect the wire
harness connector.
(6) Separate the console floor air duct from the air
outlet duct (Fig. 8).
(7) Remove the console and air duct from the floor.
(8) Separate the floor air duct from the console.
(9) Remove the retaining screws and detach the
floor duct from the heater housing, if necessary.
(10) Remove the console support brackets.
The brackets are attached directly to the
floor panel below the carpet.
INSTALLATION
(1) Install the console support brackets, if re-
moved. Tighten the screws to 1 Nzm (11 In-lbs)
torque.
The brackets are attached directly to the
floor panel below the carpet.(2) Attach the floor duct to the heater housing, if
removed. Tighten the screws to 1 Nzm (11 In-lbs)
torque.
(2) Attach the air duct to the console.
(3) Position the console on the floor, attach the air
duct to the air outlet duct, connect the wire harness
connector and install the console retaining screws in
the brackets. Tighten the screws to 1 Nzm (11 In-lbs)
torque.
(4) Install the console cover and shift indicator be-
zels (or cover plate). Tighten the screws to 1 Nzm(11
In-lbs) torque.
(5) If equipped:
²Connect the wire harness connector to the outside
mirror remote control switch.
²Insert the switch into the console hole.
²Push inward to engage the retaining clips.
(6) Install the shift lever handle/knob.
JACK STORAGEÐXJ
The XJ lift jack and related tools are stored under
the rear seat behind the front passenger's seat. The
jack and tools are attached to the floor panel and
seat cushion crossmember with a retainer and hold-
down bolt (Fig. 1).
When necessary, the jack retainer bracket can be
removed from the crossmember by drilling-out the
rivet heads and then removing the rivet bodies with
a punch. Install the retainer bracket with either riv-
ets or bolts and nuts (Fig. 2).
Fig. 7 Full Console Removal/Installation
Fig. 8 Air Outlet and Console Floor Air Ducts
Fig. 1 Jack and Related Tools
JINTERIOR COMPONENTSÐXJ 23 - 97

HEATING AND AIR CONDITIONING
CONTENTS
page page
COMPONENT SERVICEÐXJ VEHICLES...... 23
COMPONENT SERVICEÐYJ VEHICLES...... 32
COMPRESSOR SERVICE.................. 19
GENERAL INFORMATION.................. 1
HEATING AND AIR CONDITIONING TEST
PROCEDURES......................... 15REFRIGERANT SERVICE AND PERFORMANCE
TEST................................ 11
TORQUE SPECIFICATIONS................ 37
WARNINGS, CAUTIONS AND SERVICE
PRECAUTIONS......................... 9
GENERAL INFORMATION
INDEX
page page
A/C Components.......................... 4
Heater and A/C Operation.................... 1
Manifold Gauge Set........................ 7Refrigerant............................... 7
Refrigerant Equipment...................... 7
HEATER AND A/C OPERATION
HEATERÐXJ
A blend-air heating system is used in XJ vehicles.
The temperature of heated air is controlled by regu-
lating the quantity of air flow through the heater
core. This is accomplished by blending outside air
with heated air from the heater core to obtain the de-
sired discharge temperature. A temperature control
lever on the heater control determines air flow
through the heater core. The lever uses a cable to op-erate the blend-air door. This door controls air flow
through the core. Vacuum motors are used to actuate
and position the remaining door in the system.
On left hand drive (LHD) XJ vehicles a water valve
controls coolant flow to the heater core. The valve is
vacuum operated. When vacuum is applied, the valve
opens and coolant is directed through the heater core
and back to the engine. When the water valve is
closed (no vacuum applied) coolant flow bypasses the
heater core back to the engine.
JHEATING AND AIR CONDITIONING 24 - 1

HEATERÐYJ
A blend-air heating system is used in YJ vehicles.
The blend-air system provides a constant flow of en-
gine coolant through the heater core.
The air control lever (Fig. 1) operates a door in the
fresh air intake duct. The door controls the amount
of fresh air flow into the heater housing and core.
When the lever is in the OFF position, the intake
door is closed preventing air flow into the housing.
The temperature control lever (Fig. 1) determines
air flow through the heater core. The lever operates
the heater housing blend-air door which controls air
flow through the core.The blower motor is operated by the control switch
(Fig. 1). The switch provides 3 blower speeds for in-
creased air flow in heat or defrost mode.
DEFROSTING
The heater housing has a defroster door to divert
heated air to the defroster duct and outlets (Fig. 2).
Defrost air flow is controlled by the air control lever.
For defroster operation, the air control lever must
be moved to the defrost detent. The detent is identi-
fied by the defrost symbol on the control panel. In
this position, the defroster door diverts the heated
air from the core to the defroster duct outlets.
If air control lever is moved to any position be-
tween heat and defrost, the defroster door does not
close completely. In this mode, the door remains par-
tially open causing heated air to be divided equally
between the heat and defrost outlets.
FRESH AIR VENTILATION
The fresh air ventilating system (Fig. 3) is operated
by the air control lever. When the lever is moved to
VENT position, outside air from the cowl intake
flows into the heater housing. Incoming air is di-
rected into the vehicle interior through vent doors in
the housing.
A door in the intake duct controls air flow into the
duct. The door is operated by a vacuum motor. The
Fig. 2 Heating System Components
Fig. 1 Heater Control Panel
JHEATING AND AIR CONDITIONING 24 - 3

motor is controlled by a vacuum switch in the heater
control panel. The vent air doors are opened and
closed by a cable and linkage operated by the air con-
trol lever. Fresh air intake occurs only when the le-
ver is in the VENT position.
AIR CONDITIONING
The compressor increases the pressure and temper-
ature of the refrigerant. The heated refrigerant vapor
is pumped into the condenser where it is cooled by
air passing over the condenser fins. As the refriger-
ant cools in the condenser, it condenses into a liquid.
Still under high pressure, the liquid refrigerant
passes into the receiver. The receiver acts as a reser-
voir to furnish refrigerant to the expansion valve at
all times. From the receiver, the high pressure liquid
refrigerant passes to the expansion valve. The expan-
sion valve meters refrigerant into the evaporator.
The low pressure is maintained by the suction side of
the compressor. As it enters the evaporator, the re-
frigerant begins to absorb heat from the air passing
over the evaporator core. Having given up its heat to
boil the refrigerant, the air is cooled and passes into
the passenger compartment. From the evaporator the
vaporized refrigerant is drawn back to the compres-
sor to repeat the cycle.
A/C COMPONENTS
COMPRESSOR:The SD7H15 Compressor is used
on all models. The purpose of the compressor is to
compress the low-pressure refrigerant vapor into a
high pressure, high temperature vapor. The compres-
sor is serviced as a assembly only.
CLUTCH PULLEY AND COIL:They are
mounted on the compressor and providing a way to
drive the compressor. The compressor clutch and coil
are the only serviced parts on the SD7H15 compres-
sor. When the compressor is not in operation, the
pulley free wheels on the clutch hub bearing. When
the coil is energized the clutch plate is magnetically
engaged with the pulley and turns the compressor
shaft.
CONDENSER:The condenser is located in front of
the engine radiator. Its function is to cool the hot
high pressure refrigerant gas. This causes it to con-
dense into high pressure liquid refrigerant.
EXPANSION VALVE:The expansion valve is lo-
cated in the engine compartment on XJ vehicles. On
YJ vehicles it is located behind the A/C housing. Its
function is to meter refrigerant into the evaporator in
accordance with cooling requirements.
Fig. 3 Fresh Air Intake System Components
24 - 4 HEATING AND AIR CONDITIONINGJ

REFRIGERANT OIL
It is important to have the correct amount of oil in
the A/C system. This will ensure proper lubrication of
the compressor. Too little oil will result in damage to
the compressor. Too much oil will reduce the cooling
capacity of the system.
The oil used in the SD7H15 compressor is a poly-
alkylene glycol synthetic oil SP-20 PAG, wax-free re-
frigerant oil. Only refrigerant oil of the same type
should be used to service the system. Do not use any
other oil. The oil container should be kept tightly
capped until it is ready for use and then capped after
use to prevent contamination. Refrigerant oil will
quickly absorb any moisture it comes in contact with.
OIL LEVEL CHECK
It will not be necessary to check oil level in the
compressor or to add oil unless there has been an oil
loss. This may be due to a rupture or leak from a
line, shaft seal, evaporator or condenser. Oil loss at a
leak point will be evident by the presence of a wet,
shiny surface around the leak.
When an A/C system is assembled at the factory,
all components (except the compressor) are refriger-
ant oil free. After the system has been charged and
operated, the oil in the compressor is dispersed
through the system. The receiver-drier, evaporator,
condenser and compressor will retain a significant
amount of oil.
Refrigerant oil must be added when a receiver-
drier, evaporator, condenser or compressor are re-
placed. When the compressor is replaced, the oil
must be drained from the replaced compressor and
measured. Drain all the oil from the new compressor.
Add back into the new compressor the amount of oil
that was drained out of the old compressor.
Add an additional 30 ml (1 fluid oz.) of com-
pressor oil to the system when a receiver-drier,
condenser or evaporator is replaced.
AIR CONDITIONING PERFORMANCE TESTS
Humidity has an important bearing on the temper-
ature of the air delivered to the vehicle's interior. It
is important to understand the effect humidity has
on the performance of the system. When humidity is
high, the evaporator has to perform a double duty. It
must lower the air temperature and the temperature
of the moisture carried in the air. Condensing the
moisture in the air transfers a great deal of heat en-
ergy into the evaporator fins and tubing. This re-
duces the amount of heat the evaporator can absorb
from the air. High humidity greatly reduces the evap-
orator's ability to lower the temperature of the air.Evaporator capacity used to reduce the amount of
moisture in the air is not wasted. Wringing some of
the moisture out of the air entering the vehicle adds
to the comfort of the passengers. However, an owner
may expect too much from their air conditioning sys-
tem on humid days. A performance test is the best
way to determine whether or not the system is per-
forming up to standard. This test also provides valu-
able clues to the possible cause of trouble.
Air temperature in test room must be 21ÉC (70ÉF)
minimum for this test.
(1) Connect a Tachometer and manifold gauge set.
(2) Set A/C controls to Max A/C, temperature lever
on full cool and blower on high.
(3) Start engine and adjust idle to 1,000 RPM with
A/C clutch engaged.
(4) Engine should be warmed up with doors, win-
dows and hood closed.
(5) Insert a thermometer in the left center A/C out-
let. Operate the A/C and engine for 5 minutes. The
A/C clutch may cycle depending on ambient temper-
atures.
(6) After 5 minutes note the discharge air temper-
ature. If the clutch cycles, take the reading before
the clutch disengages.
(7) On LHD XJ vehicles open the hood and discon-
nect vacuum line going to the heater water control
valve. Observe the valve arm for movement as the
line is disconnected. Plug the vacuum line to prevent
leakage. If it does not move repair vacuum circuit.
(8) Operate the A/C for 2 more minutes and take
the discharge air temperature reading again. On XJ
vehicles if the temperature increased by more than
2ÉC (5ÉF) check the blend air door cable for correct
operation.
(9) Compare the discharge air temperature to the
A/C Performance (Temperature and Pressure) Chart.
If the discharge air temperature is high, refer to Re-
frigerant Leak Testing and Refrigerant System Diag-
nosis Chart.
(10) Compare the compressor discharge and suc-
tion pressures to the A/C Performance (Temperature
and Pressure) Chart. If the compressor discharge or
suction pressure is not normal, check the operation of
the refrigerant system. Refer to Refrigerant System
Diagnosis Chart.
If pressures are abnormal, refer to the Pressure
and Performance Diagnosis Charts.
The following chart have been developed for quick
reference.
24 - 12 HEATING AND AIR CONDITIONINGJ

HEATING AND AIR CONDITIONING TEST PROCEDURES
INDEX
page page
A/C Compressor Clutch..................... 15
A/C Compressor Clutch Relay................ 15
A/C Compressor Clutch Relay................ 16
Air Conditioning ControlsÐXJ Vehicles......... 15
Air Conditioning ControlsÐYJ Vehicles......... 16
Blower Motor............................ 17
Blower Motor Switch....................... 16Compressor Clutch........................ 16
Fin Sensing Cycling Clutch Switch............. 15
Heater Diagnosis......................... 17
Low-Pressure High-Pressure Cut-Off Switch..... 15
Low-Pressure High-Pressure Cut-Off Switch..... 16
Thermostatic Control....................... 16
AIR CONDITIONING CONTROLSÐXJ VEHICLES
The A/C Compressor Clutch is controlled by several
components: the Pressure Cut-Off Switch, Cycling
Clutch Switch, Clutch Relay and Powertrain Control
Module (PCM).
Powertrain Control Module may delay A/C clutch
engagement up to 30 seconds.
Refer to Group 8W Wiring Diagrams for wiring and
terminals. Use volt ohmmeter to test switches.
A/C COMPRESSOR CLUTCH
The clutch assembly consists of a stationary elec-
tromagnetic coil, hub bearing pulley assembly, and
clutch plate. When the coil is energized the plate is
magnetically engaged with the pulley and turns the
compressor shaft.
A/C COMPRESSOR CLUTCH TEST
(1) Unplug clutch coil connector.
(2) Connect a jumper wire from the battery posi-
tive post to the clutch coil terminal. The clutch
should engage, if not leave jumper wire connected
and go to next step.
(3) Connect a jumper wire from clutch coil frame to
chassis ground. The clutch should engage if not re-
pair clutch coil ground or replace coil.
A/C COMPRESSOR CLUTCH RELAY
The A/C compressor clutch relay controls the 12-
volt source to the A/C clutch. The relay is activated
when the PCM receives a A/C request signal from the
fin-sensed cycling clutch switch. The PCM then sends
a ground signal to the relay. The relay is activated
and sends 12-volts to the clutch coil which energizes
the clutch. The relay is located in the power distribu-
tion center.
COMPRESSOR CLUTCH RELAY TEST
For test procedure refer to Powertrain Diagnostic
Service Manual for A/C clutch relay circuit test.
LOW-PRESSURE HIGH-PRESSURE CUT-OFF
SWITCH
The pressure cut-off switch is located on the filter
drier and is wired in series with compressor clutch.
The switch interrupts the power to the compressor
clutch circuit when the pressure drops to 193 kPa (28
psi) or increases above 3100 to 3375 kPa (450 to 490
psi).
PRESSURE CUT-OFF SWITCH TEST
(1) Verify system has correct refrigerant charge.
(2) Turn ignition switch to RUN, A/C blower switch
to ON and control set to MAX.
(3) Unplug pressure cut-off switch and test feed
circuit from select switch. It should be battery volt-
age if not, repair open to select switch.
(4) Test for continuity between the switch termi-
nals. If continuity is not present recover refrigerant
from the system. Replace switch, evacuate and re-
charge system.
FIN SENSING CYCLING CLUTCH SWITCH
The switch is attached to the evaporator coil with
the temperature sensing probe inserted into the coil
fins. This switch prevents condensate water on the
evaporator coil from freezing. It does this by sending
signals to the PCM to cycling the compressor clutch
on and off.
FIN-SENSED CYCLING CLUTCH SWITCH TEST
Test area ambient temperature should be around
21ÉC (70ÉF) for test.
(1) Verify system has correct refrigerant charge.
(2) Start Engine and turn on A/C.
(3) If the compressor clutch cycles ON and OFF 2
to 3 times per minute the cycling clutch switch is
normal. The ambient temperature should be between
20ÉC-30ÉC (68ÉF-90ÉF). Above 32ÉC (90ÉF) the com-
pressor clutch may stay engaged (non cycling) due to
the high heat load, this condition is normal. If the
compressor clutch fails to engage go to next step.
(4) Disconnect wiring harness connector from
switch. With a volt meter test feed circuit from cut-
JHEATING AND AIR CONDITIONING 24 - 15

(6) Test A/C blower switch HIGH terminal with
blower switch in HIGH, should be battery voltage. If
not, replace switch.
BLOWER MOTOR
The A/C blower motor is attached to the evaporator
housing mounted under the instrument panel. The
motor has a ground wire and 3 wires connect to the
motor brushes. When voltage is applied to the sepa-
rate brushes it provides the 3 blower speeds LO,
MED, and HIGH.
BLOWER MOTOR TEST
Turn ignition switch to RUN for voltage tests and
turn ignition switch to OFF for resistance test.
(1) Test A/C blower motor ground terminal should
be 0 ohms. If not, repair ground circuit.
(2) Test A/C blower motor connector LO terminal
with blower switch in LO, should be battery voltage.
If not repair open from blower switch. If the blower
motor is still inoperative replace motor.
(3) Test A/C blower motor connector MED terminal
with blower switch in MED, should be battery volt-
age. If not repair open from blower switch. If the
blower motor is still inoperative replace motor.
(4) Test A/C blower motor connector HIGH termi-
nal with blower switch in HIGH, should be battery
voltage. If not, repair open from blower switch. If the
blower motor is still inoperative, replace motor.
HEATER DIAGNOSIS
On LHD XJ vehicles a water valve controls coolant
flow to the heater core. The valve is vacuum oper-
ated. When vacuum is applied, the valve opens and
coolant is directed through the heater core and back
to the engine. When the water valve is closed (no
vacuum applied) coolant flow bypasses the heater
core back to the engine.
The heating system receives its battery feed from
the fuse box. On YJ vehicles the feed circuit runs to
the HEATER/OFF switch and then to the BLOWER
switch. On XJ vehicles the feed circuit runs to the
HEAT/MODE switch and then to the BLOWER
switch.
The blower speed is controlled by the blower switch
and blower resistors. With the switch in LO, battery
voltage is supplied to the motor through all of the re-
sistors. The motor runs slowly. When the blower
switch is moved to a higher speed, battery voltage in-
creases to the blower motor which increase its speed.
This is accomplished by bypassing some of the blower
resistors. When the switch is in HI, blower resistors
are bypassed and battery voltage is applied directly
to the blower motor.
The following chart has been developed for quick
reference.
Refer to the Group 8W Wiring Diagrams for com-
plete wiring schematic.
JHEATING AND AIR CONDITIONING 24 - 17