1995 JEEP YJ heating

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

XJ PERFORMANCE TEMPERATURE AND PRESSURE CHART
YJ PERFORMANCE TEMPERATURE AND PRESSURE CHART
JHEATING AND AIR CONDITIONING 24 - 13

PRESSURE DIAGNOSIS
PERFORMANCE DIAGNOSIS
24 - 14 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

off switch for battery voltage. If no voltage is present
test pressure cut-off switch. If voltage is present go
to next step.
(5) With ohmmeter test harness connector ground
circuit for continuity to ground. If circuit is open, (no
continuity) repair ground circuit. If circuit test OK
and clutch does not engage refer to Powertrain Diag-
nostic Service Manual for A/C clutch circuit test.
AIR CONDITIONING CONTROLSÐYJ VEHICLES
The air conditioning circuit consists of 3 segments;
battery supply, blower motor and compressor clutch.
The 3 segments have a common connection point at
the blower switch.
The power supply circuit extends from the HTR/
FAN fuse to the blower switch. From the blower
switch, battery feed is routed to the blower motor
and compressor clutch circuit.
Refer to Group 8W Wiring Diagrams for wiring
schematic and terminals. Use volt ohmmeter to test
switches.
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.
COMPRESSOR CLUTCH TEST
(1) Unplug clutch coil connector.
(2) Connect jumper wire from battery positive post
to clutch coil connector. The clutch should engage, if
not leave jumper wire connected and go to next step.
(3) Connect 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. The
PCM then sends a ground signal to the relay. The re-
lay is activated and sends 12-volts to the clutch coil
which energizes the clutch. The relay is located in
the power distribution 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 compressorclutch 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) Turn ignition switch to RUN, A/C blower switch
to ON and control set to MAX.
(2) Unplug pressure cut-off switch connector and
test feed circuit from the thermostatic, should be bat-
tery voltage. If not, proceed to thermostatic control
tests.
(3) Test for continuity between the switch termi-
nals. If continuity is not present recover refrigerant
system, replace switch, evacuate and recharge sys-
tem.
THERMOSTATIC CONTROL
Cycling of the compressor and therefore the tem-
perature of the outlet air is regulated by the thermo-
static control. A thermal sensor extends from the
control to the evaporator housing. When the temper-
ature of the evaporator drops below the set tempera-
ture, the thermostatic control opens the clutch
circuit. The circuit remains open until evaporator
temperature rises above the set temperature.
THERMOSTATIC CONTROL TEST
(1) Turn ignition switch to RUN, A/C blower switch
to ON and thermostatic control set to MAX cool.
(2) Test thermostatic control feed terminal from
blower switch, should be battery voltage. If not re-
pair open from blower switch.
(3) Test thermostatic control output terminal to
pressure cut-out switch, should be battery voltage. If
not, replace thermostatic control.
BLOWER MOTOR SWITCH
The blower switch controls blower motor speed.
The blower motor segment consists of the 3 wires
from the blower switch to the motor. Through the
switch, the 3 wires connect the motor brushes to bat-
tery supply. When connected to battery feed, the sep-
arate brushes provide the 3 blower speeds LO, MED,
and HIGH.
BLOWER MOTOR SWITCH TEST
(1) Turn ignition to RUN position.
(2) Test battery side of fuse for battery voltage. If
not, repair open from ignition switch.
(3) Test A/C blower switch feed circuit from fuse
box should be battery voltage. If not, repair open
from fuse panel.
(4) Test A/C blower switch LO terminal with
blower switch in LO, should be battery voltage. If
not, replace switch.
(5) Test A/C blower switch MED terminal with
blower switch in MED, should be battery voltage. If
not, replace switch.
24 - 16 HEATING AND AIR CONDITIONINGJ

(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