heating JEEP CHEROKEE 1995 Service Service Manual

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

AIR CONDITIONING SCHEMATICÐXJ
JHEATING AND AIR CONDITIONING 24 - 5

EVAPORATIVE HOUSING COMPONENTSÐYJ
24 - 6 HEATING AND AIR CONDITIONINGJ

EVAPORATOR COIL:The coil is located in the
A/C housing. Its function is to remove heat and de-
humidify the air before it enters the vehicle.
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 controls evaporator temperature and pre-
vents condensate water on the evaporator coil from
freezing. It does this by sending signals to the Pow-
ertrain Control Module (PCM) to cycling the com-
pressor clutch on and off. This switch is used onXJ
only.
FILTER-DRIER:The drier is used to remove any
traces of moisture from the refrigerant system. A
sight glass is located on top of the filter drier. It is
used as a diagnostic tool to observe refrigerant flow.
HIGH PRESSURE RELIEF VALVE:The valve is
located on the filter drier. The valve is used to pre-
vent excessive high pressure build of 3445 to 4135
kPa (500 to 600 psi) and above. This prevents dam-
age to the compressor and other system components.
LOW-PRESSURE HIGH-PRESSURE CUT-OFF
SWITCH:The switch is located on the filter drier
and is wired in series with compressor clutch. When
the pressure drops down to 193 kPa (28 psi) the
switch interrupts the power to the compressor clutch.
When the pressure increases above 3100 to 3375 kPa
(450 to 490 psi) the switch interrupts the power to
the compressor clutch.
THERMOSTAT:The thermostat is located in the
evaporator housing. The thermostat temperature
sensing probe is inserted into the evaporator coil. Its
function is to cycles the compressor clutch on and off.
This switch controls temperature and prevents con-
densate water on the evaporator coil from freezing.
The thermostat is used on theYJonly.
REFRIGERANT LINES:The lines are used to
carry the refrigerant between the various system
components.
SERVICE PORTS:The high pressure service port
is located on the discharge line near the compressor.
The low pressure service port is located on the suc-
tion line near the compressor. These ports are used
to attach A/C gauges. After servicing the refrigerant
system, always install service port caps.
REFRIGERANT
XJ and YJ vehicles use a new type of refrigerant
called R-134a. It is a non-toxic, non-flammable, clear
color-less liquified gas.
R-134a refrigerant is not compatible with R-12 re-
frigerant. A small amount of R-12 in a R-134a system
will cause compressor failure, oil sludge or poor air
conditioning performance.R-134a refrigerant requires a special type of com-
pressor oil (SP20 PAG). When adding oil, make sure
that it is designed to be used in a R-134a system and
the SD7H15 compressor.
Service ports have been designed to ensure that
the system is not accidentally filled with R-12 refrig-
erant.
REFRIGERANT EQUIPMENT
WARNING: EYE PROTECTION MUST BE USED
WHEN SERVICING AN AIR CONDITIONING REFRIG-
ERANT SYSTEM. TURN OFF (ROTATE CLOCKWISE)
ALL VALVES ON THE EQUIPMENT BEING USED
BEFORE PROCEEDING WITH THIS OPERATION.
PERSONNEL INJURY CAN RESULT.
Chrysler Corporation recommends a (R-134a) recy-
cling device that meets SAE standard J2210 be used
when servicing the refrigerant system. Contact an
automotive service equipment supplier for refrigerant
recycling equipment that is available in your area.
Refer to the operating instructions provided with the
recycling equipment for proper operation.
MANIFOLD GAUGE SET
CAUTION: DO NOT use an R-12 manifold gauge set
on an R-134a system. The refrigerants are not com-
patible and system damage will result.
A manifold gauge set (Fig. 1) may be needed in
conjunction with the charging and or recovery/recy-
cling device. The service hoses on the gauge set being
used should have manual (turn wheel) or automatic
back flow valves at the service port connector ends.
This will prevent refrigerant from being release into
the atmosphere.
LOW PRESSURE GAUGE HOSE
The low pressure hose (BLUE with BLACK STRIP)
should be attached to the charging/service port. This
port is located at the right front of the engine com-
partment in the condenser-to-evaporator line.
HIGH PRESSURE GAUGE HOSE
The high pressure hose (RED with BLACK STRIP)
should be attached to the discharge/service port. This
port is located on the compressor plumbing or mani-
fold.
RECOVERY/RECYCLING/EVACUATION/
CHARGING HOSE
The center manifold hose (YELLOW or WHITE
with BLACK STRIP) is used to recover, evacuate and
charge the refrigerant system. When the low or high
pressure valves on the manifold gauge set are
opened, the refrigerant in the system will escape
through this hose.
JHEATING AND AIR CONDITIONING 24 - 7

Refer to the Recovery/Recycling device operators
manual for proper procedures.
Fig. 1 Manifold Gauge Set
24 - 8 HEATING AND AIR CONDITIONINGJ

WARNINGS, CAUTIONS AND SERVICE PRECAUTIONS
WARNINGS
WARNING: THE AIR CONDITIONING SYSTEM CON-
TAINS REFRIGERANT UNDER HIGH PRESSURE.
SEVERE PERSONAL INJURY MAY RESULT FROM
IMPROPER SERVICE PROCEDURES. REPAIRS
SHOULD ONLY BE PERFORMED BY QUALIFIED
SERVICE PERSONNEL.
WARNING: AVOID BREATHING A/C REFRIGERANT
AND LUBRICANT VAPOR OR MIST. EXPOSURE MAY
IRRITATE EYES, NOSE AND/OR THROAT. WEAR
EYE PROTECTION WHEN SERVICING THE AIR
CONDITIONING REFRIGERANT SYSTEM. SERIOUS
EYE INJURY CAN RESULT FROM EYE CONTACT
WITH REFRIGERANT. IF EYE CONTACT IS MADE,
SEEK MEDICAL ATTENTION IMMEDIATELY.
WARNING: DO NOT EXPOSE REFRIGERANT TO
OPEN FLAME. POISONOUS GAS IS CREATED
WHEN REFRIGERANT IS BURNED. AN ELEC-
TRONIC TYPE LEAK DETECTOR IS RECOM-
MENDED.
WARNING: IF ACCIDENTAL SYSTEM DISCHARGE
OCCURS, VENTILATE THE WORK AREA BEFORE
RESUMING SERVICE. LARGE AMOUNTS OF RE-
FRIGERANT RELEASED IN A CLOSED WORK AREA
WILL DISPLACE THE OXYGEN AND CAUSE SUFFO-
CATION.
WARNING: THE EVAPORATION RATE OF (R-134A)
REFRIGERANT AT AVERAGE TEMPERATURE AND
ALTITUDE IS EXTREMELY HIGH. AS A RESULT,
ANYTHING THAT COMES IN CONTACT WITH THE
REFRIGERANT WILL FREEZE. ALWAYS PROTECT
SKIN OR DELICATE OBJECTS FROM DIRECT CON-
TACT WITH REFRIGERANT.
WARNING: R-134A SERVICE EQUIPMENT OR VEHI-
CLE A/C SYSTEM SHOULD NOT BE PRESSURE
TESTED OR LEAK TESTED WITH COMPRESSED
AIR. SOME MIXTURES OF AIR AND R-134A HAVE
BEEN SHOWN TO BE COMBUSTIBLE AT ELEVATED
PRESSURES. THESE MIXTURES ARE POTENTIALLY
DANGEROUS AND MAY RESULT IN FIRE OR EX-
PLOSION CAUSING INJURY OR PROPERTY DAM-
AGE.
CAUTIONS
CAUTION: Liquid refrigerant is corrosive to metal
surfaces. Follow the operating instructions supplied
with equipment being used.
CAUTION: DO NOT use R-12 equipment or parts on
the R-134a system. Damage to the system will re-
sult.
CAUTION: Never add R-12 to a system designed to
use R-134a. Damage to the system will result.
CAUTION: R-12 compressor oil can not be mixed
with the R-134a compressor oil. They ARE NOT
compatible.
CAUTION: Do not over charge refrigerant system.
This will cause excessive compressor head pres-
sure and can cause noise and system failure.
SERVICE PRECAUTIONS
Recover the refrigerant before opening any fitting
or connection. Open fittings with caution even after
the system has been discharged. Never open or
loosen a connection before recovering the refrigerant.
The A/C system must always be evacuated before
charging.
DO NOT open the refrigerant system or uncap a
replacement component until you are ready to service
the system. This will prevent contamination in the
system.
Before disconnecting a component clean the outside
of the fittings thoroughly to prevent contamination
entering the system.
Immediately after disconnecting a component from
the system, seal the open fittings with a cap or plug.
Before connecting an open fitting always install a
new seal/gasket. Coat the fitting and seal with clean
refrigerant oil before connecting.
When installing a refrigerant line avoid sharp
bends. Position the lines away from the exhaust or
any sharp edges which may chafe the line.
Tighten fittings only to the specified torque. The
aluminum fittings used in the A/C system will not
tolerate over tightening.
When disconnecting a fitting use a wrench on both
halves of the fitting. This will prevent twisting of the
refrigerant lines or tubes.
Refrigerant oil absorbs moisture from the atmo-
sphere if left uncapped. DO NOT open a container of
JHEATING AND AIR CONDITIONING 24 - 9

oil until you are ready to use it. Install the cap im-
mediately after using. Store the oil only in a clean
moisture-free container.
Keep service tools and the work area clean. Con-
tamination of A/C system through careless work hab-
its must be avoided.
COOLING SYSTEM
To maintain the performance level of the heating/
air conditioning system, the engine cooling system
must be properly maintained.
The use of a bug screen is not recommended. Any
obstructions in front of the radiator or condenser can
reduce the performance of the A/C and cooling sys-
tem. If a bug screen is used it must be cleaned fre-
quently.
COOLANT PRECAUTIONS
WARNING: ANTIFREEZE IS AN ETHYLENE GLYCOL
BASE COOLANT AND IS HARMFUL IF SWAL-
LOWED OR INHALED. IF SWALLOWED, DRINK
TWO GLASSES OF WATER AND INDUCE VOMIT-
ING. IF INHALED, MOVE TO FRESH AIR AREA.
SEEK MEDICAL ATTENTION IMMEDIATELY.
WARNING: WASH SKIN AND CLOTHING THOR-
OUGHLY AFTER COMING IN CONTACT WITH ETH-
YLENE GLYCOL.
WARNING: KEEP OUT OF REACH OF CHILDREN
AND PETS.
WARNING: DO NOT OPEN A COOLING SYSTEM
WHEN THE ENGINE IS AT RUNNING TEMPERA-
TURE. PERSONAL INJURY CAN RESULT.WARNING: DO NOT STORE IN OPEN OR UN-
MARKED CONTAINERS.
WARNING: HOT ENGINE COOLANT CAN CAUSE
SEVERE BURNS. DO NOT OPEN THE RADIATOR
DRAIN COCK WHEN THE COOLING SYSTEM IS
HOT AND PRESSURIZED. ALLOW THE COOLANT
TO DECREASE TO ROOM TEMPERATURE BEFORE
STARTING REPAIR OPERATIONS.
The engine cooling system is designed to develop
internal pressure of 97 to 124 kPa (14 to 18 psi). Al-
low the vehicle 15 minutes to cool down (or until a
safe temperature and pressure are attained) before
opening the cooling system. Refer to Group 7, Cooling
System.REFRIGERANT HOSES/TUBES PRECAUTIONS
Kinks or sharp bends in the refrigerant tubing or
hoses will reduce the capacity of the entire system.
High pressures are produced in the system when it is
operating. Extreme care must be exercised to make
sure that all connections are pressure tight. Dirt and
moisture can enter the system when it is opened for
repair.
A good rule for the flexible hose lines is to keep the
radius of all bends at least 10 times the diameter of
the hose. Sharp bends will reduce the flow of refrig-
erant. The flexible hose lines should be routed so
they are at least 80 mm (3 inches) from the exhaust
manifold. It is a good practice to inspect all flexible
hose lines at least once a year to make sure they are
in good condition and properly routed.
24 - 10 HEATING AND AIR CONDITIONINGJ

REFRIGERANT SERVICE AND PERFORMANCE TEST
INDEX
page page
Air Conditioning Performance Tests............ 12
Charging Refrigerant System................. 11
Evacuating Refrigerant System............... 11Leak Testing Refrigerant.................... 11
Recovering Refrigerant System............... 11
Refrigerant Oil........................... 12
LEAK TESTING REFRIGERANT
REVIEW WARNINGS AND CAUTIONS IN
THIS GROUP BEFORE LEAK TESTING.
If A/C system is not cooling properly, determine if
system is fully charged. Refer to Refrigerant System
Diagnosis Chart. If the system is empty evacuate the
A/C system and charge system with 0.283 kPa (0.6
lbs. or 10 oz.) R-134a refrigerant. Refer to Charging
Refrigerant System for instructions. To detect a leak
in the system, perform the following procedures.
(1) Position the vehicle in a wind free work area.
This will aid in detecting small leaks.
(2) Bring A/C system up to operating temperature
and pressure. This is done by allowing the engine to
run with the A/C on for 5 to 7 minutes.
(3) Open hood 5 minutes prior to leak test. This
will dissipate any accumulated refrigerant in the en-
gine compartment.
(4) With the engine not running, use an R-134a
Electronic Leak Detector and search for leaks. Move
probe slowly along the bottom side of lines and fit-
tings, because R-134a is heavier than air. Fittings,
lines, or components that appear to be oily usually
indicates a refrigerant leak.
(5) To inspect the evaporator core for leaks. Set the
blower at low speed and the selector in PANEL and
RECIRC mode check for leaks at CENTER panel out-
lets.
RECOVERING REFRIGERANT SYSTEM
REVIEW WARNINGS AND CAUTIONS IN
GENERAL INFORMATION SECTION OF THIS
GROUP BEFORE DISCHARGING SYSTEM.
R-134a refrigerant is a hydrofluorocarbon (HFC)
that does not contain chlorine. R-134a refrigerant Re-
covery/Recycling Station that meets SAE standard
J2210 must be used to recover the refrigerant. Refer
to the operating instructions provided with the equip-
ment for proper operation.
EVACUATING REFRIGERANT SYSTEM
REVIEW WARNINGS AND CAUTIONS IN
GENERAL INFORMATION SECTION OF THIS
GROUP BEFORE EVACUATING SYSTEM.
If the A/C system has been open to the atmosphere,
it must be evacuated before the system can be
charged. Moisture and air mixed with refrigerant will
raise the compressor head pressure above acceptable
operating levels. This will reduce the performance of
the air conditioner and damage the compressor. Mois-
ture will boil at near room temperature when ex-
posed to vacuum. To evacuate the refrigerant system
use following procedure:
(1) Connect a suitable charging station and mani-
fold gauge set to the vehicle.
(2) Open the low and high side valves and start
vacuum pump. When suction gauge reads 88 kPa (26
in. Hg) vacuum or greater, close all valves and turn
off vacuum pump. If system fails to reach specified
vacuum, the system has a leak that must be cor-
rected. If system maintains the specified vacuum for
30 minutes, start the vacuum pump. Then open the
suction and discharge valves and evacuate an addi-
tional 10 minutes.
(3) Close all valves. Turn off and disconnect the
vacuum pump.
The system is now ready to be charged with refrig-
erant.
CHARGING REFRIGERANT SYSTEM
REVIEW WARNINGS AND CAUTIONS IN
GENERAL INFORMATION SECTION OF THIS
GROUP BEFORE CHARGING SYSTEM.
After the system has been tested for leaks and
evacuated, a refrigerant charge can be injected into
the system. Refer to refrigerant capacities for proper
amount of refrigerant charge. Charge the system us-
ing a Recovery/Recycling/Charging Station approved
for R-134a refrigerant. Refer to the instructions pro-
vided with the equipment for proper operation.
REFRIGERANT CHARGE CAPACITY
The R-134a system charge capacity is 0.9 kPa (32
oz.) for XJ and YJ vehicles.
JHEATING AND AIR CONDITIONING 24 - 11

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