2. FLOOR/PANEL DOOR
HEATER CORE BLEND-AIR DOOR AIR
RECIRCULATING A/C
DOOR ONLY
FLOOR/DE- EVAPORATOR A/C
FROST ONLY
DOOR
24 - 2 HEATING AND AIR CONDITIONING XJ
GENERAL INFORMATION use engine vacuum to control the mode doors through
vacuum actuator motors.
HEATER AND AIR CONDITIONER On air conditioned vehicles, the outside air intake
All vehicles are equipped with a common heater- can be shut off by selecting the Recirculation Mode
A/C housing assembly (Fig. 1). The system combines with the mode control knob. This will open a vacuum
air conditioning, heating, and ventilating capabilities actuated recirculating air door and recirculate the air
in a single unit housing mounted under the instru- that is already inside the vehicle.
ment panel. On heater-only systems, the evaporator The optional air conditioner for all models is
coil and recirculating air door are omitted from the designed for the use of non-CFC, R-134a refrigerant.
housing. The air conditioning system has an evaporator to cool
and dehumidify the incoming air prior to blending it
with the heated air. This system uses a fixed orifice
tube in the liquid line near the condenser outlet tube
to meter refrigerant flow to the evaporator coil. To
maintain minimum evaporator temperature, a fixed
pressure setting switch on the accumulator cycles the
compressor clutch.
NOTE: This group covers both Left-Hand Drive
(LHD) and Right-Hand Drive (RHD) versions of this
model. Whenever required and feasible, the RHD
Fig. 1 Common Blend-Air Heater-Air Conditioner versions of affected vehicle components have been
System - Typical constructed as mirror-image of the LHD versions.
Outside fresh air enters the vehicle through the While most of the illustrations used in this group
cowl top opening at the base of the windshield, and represent only the LHD version, the diagnostic and
passes through a plenum chamber to the heater-A/C service procedures outlined can generally be
system blower housing. Air flow velocity can then be applied to either version. Exceptions to this rule
adjusted with the blower motor speed selector switch have been clearly identified as LHD or RHD, if a
on the heater-A/C control panel. The air intake open- special illustration or procedure is required.
ings must be kept free of snow, ice, leaves, and other
obstructions for the heater-A/C system to receive a
sufficient volume of outside air. HEATER AND AIR CONDITIONER CONTROL
The heater and optional air conditioner are blend- Both the heater-only and heater-A/C systems use a
air type systems. In a blend-air system, a blend-air combination of mechanical, electrical, and vacuum
door controls the amount of unconditioned air (or controls. These controls provide the vehicle operator
cooled air from the evaporator on models with air with a number of setting options to help control the
conditioning) is allowed to flow through, or around, climate and comfort within the vehicle. Refer to the
the heater core. A temperature control lever on the owner’s manual for more information on the sug-
heater-A/C control panel determines the discharge gested operation and use of these controls.
air temperature by moving a cable, which operates The heater-only or heater-A/C control panel is
the blend-air door. This allows an almost immediate located to the right of the instrument cluster on the
manual control of the output air temperature of the instrument panel. The control panel contains a rotat-
system. ing-type temperature control knob, a rotating-type
The mode control knob on the heater-A/C control mode control switch knob, and a rotating-type blower
panel is used to direct the conditioned air to the motor switch knob.
selected system outlets. Both mode control switches The heater-only or heater-A/C control panel cannot
be repaired. If faulty or damaged, the entire unit
must be replaced.
3. XJ HEATING AND AIR CONDITIONING 24 - 3
GENERAL INFORMATION (Continued)
SERVICE WARNINGS AND PRECAUTIONS • Do not overcharge the refrigerant system. This
will cause excessive compressor head pressure
WARNING: and can cause noise and system failure.
• THE AIR CONDITIONING SYSTEM CONTAINS
REFRIGERANT UNDER HIGH PRESSURE. SEVERE In addition to the warnings and cautions listed above,
PERSONAL INJURY MAY RESULT FROM IMPROPER the following precautions must also be observed when-
SERVICE PROCEDURES. REPAIRS SHOULD ONLY ever servicing the air conditioning system:
BE PERFORMED BY QUALIFIED SERVICE PERSON- • Recover the refrigerant before opening any fit-
NEL. ting or connection. Open the fittings with caution,
• AVOID BREATHING THE REFRIGERANT AND even after the system has been discharged. Never
REFRIGERANT OIL VAPOR OR MIST. EXPOSURE open or loosen a connection before recovering the
MAY IRRITATE THE EYES, NOSE, AND/OR THROAT. refrigerant.
WEAR EYE PROTECTION WHEN SERVICING THE • The refrigerant system must always be evacu-
AIR CONDITIONING REFRIGERANT SYSTEM. SERI- ated before charging.
OUS EYE INJURY CAN RESULT FROM DIRECT • Do not open the refrigerant system or uncap a
CONTACT WITH THE REFRIGERANT. IF EYE CON- replacement component until you are ready to service
TACT OCCURS, SEEK MEDICAL ATTENTION IMME- the system. This will prevent contamination in the sys-
DIATELY. tem.
• DO NOT EXPOSE THE REFRIGERANT TO • Before disconnecting a component, clean the out-
OPEN FLAME. POISONOUS GAS IS CREATED side of the fittings thoroughly to prevent contamina-
WHEN REFRIGERANT IS BURNED. AN ELEC- tion from entering the refrigerant system.
TRONIC LEAK DETECTOR IS RECOMMENDED. • Immediately after disconnecting a component
• IF ACCIDENTAL SYSTEM DISCHARGE from the refrigerant system, seal the open fittings
OCCURS, VENTILATE THE WORK AREA BEFORE with a cap or plug.
RESUMING SERVICE. LARGE AMOUNTS OF • Before connecting an open refrigerant fitting,
REFRIGERANT RELEASED IN A CLOSED WORK always install a new seal or gasket. Coat the fitting
AREA WILL DISPLACE THE OXYGEN AND CAUSE and seal with clean refrigerant oil before connecting.
SUFFOCATION. • Do not remove the sealing caps from a replace-
• THE EVAPORATION RATE OF R-134a REFRIG- ment component until it is to be installed.
ERANT AT AVERAGE TEMPERATURE AND ALTI- • When installing a refrigerant line, avoid sharp
TUDE IS EXTREMELY HIGH. AS A RESULT, bends that may restrict refrigerant flow. Position the
ANYTHING THAT COMES IN CONTACT WITH THE refrigerant lines away from exhaust system components
REFRIGERANT WILL FREEZE. ALWAYS PROTECT or any sharp edges, which may damage the line.
THE SKIN OR DELICATE OBJECTS FROM DIRECT • Tighten refrigerant fittings only to the specified
CONTACT WITH THE REFRIGERANT. torque. The aluminum fittings used in the refrigerant
• THE R-134a SERVICE EQUIPMENT OR THE system will not tolerate overtightening.
VEHICLE REFRIGERANT SYSTEM SHOULD NOT BE • When disconnecting a refrigerant fitting, use a
PRESSURE TESTED OR LEAK TESTED WITH COM- wrench on both halves of the fitting. This will pre-
PRESSED AIR. SOME MIXTURES OF AIR AND vent twisting of the refrigerant lines or tubes.
R-134a HAVE BEEN SHOWN TO BE COMBUSTIBLE • Refrigerant oil will absorb moisture from the
AT ELEVATED PRESSURES. THESE MIXTURES ARE atmosphere if left uncapped. Do not open a container
POTENTIALLY DANGEROUS, AND MAY RESULT IN of refrigerant oil until you are ready to use it.
FIRE OR EXPLOSION CAUSING INJURY OR PROP- Replace the cap on the oil container immediately
ERTY DAMAGE. after using. Store refrigerant oil only in a clean, air-
tight, and moisture-free container.
• Keep service tools and the work area clean. Con-
CAUTION: tamination of the refrigerant system through careless
• Liquid refrigerant is corrosive to metal sur- work habits must be avoided.
faces. Follow the operating instructions supplied
with the service equipment being used. COOLING SYSTEM REQUIREMENTS
• Never add R-12 to a refrigerant system To maintain the performance level of the heating-
designed to use R-134a. Damage to the system will air conditioning system, the engine cooling system
result. must be properly maintained.
• R-12 refrigerant oil must not be mixed with The use of a bug screen is not recommended. Any
R-134a refrigerant oil. They are not compatible. obstructions in front of the radiator or condenser will
• Do not use R-12 equipment or parts on the reduce the performance of the air conditioning and
R-134a system. Damage to the system will result. engine cooling systems.
4. 24 - 4 HEATING AND AIR CONDITIONING XJ
GENERAL INFORMATION (Continued)
COOLANT PRECAUTIONS are not reusable and new gaskets do not require
lubrication before installing.
WARNING: Using the proper tools when making a refrigerant
• ANTIFREEZE IS AN ETHYLENE GLYCOL plumbing connection is very important. Improper
BASED COOLANT AND IS HARMFUL IF SWAL- tools or improper use of the tools can damage the
LOWED OR INHALED. IF SWALLOWED, DRINK refrigerant fittings. Always use two wrenches when
TWO GLASSES OF WATER AND INDUCE VOMIT- loosening or tightening tube fittings. Use one wrench
ING. IF INHALED, MOVE TO A FRESH AIR AREA. to hold one side of the connection stationary, while
SEEK MEDICAL ATTENTION IMMEDIATELY. loosening or tightening the other side of the connec-
• WASH THE SKIN AND CLOTHING THOR- tion with a second wrench.
OUGHLY AFTER COMING IN CONTACT WITH ETH- The refrigerant must be recovered completely from
YLENE GLYCOL. the system before opening any fitting or connection.
• KEEP OUT OF THE REACH OF CHILDREN Open the fittings with caution, even after the refrig-
AND PETS. erant has been recovered. If any pressure is noticed
• DO NOT OPEN A COOLING SYSTEM WHEN as a fitting is loosened, tighten the fitting and
THE ENGINE IS AT OPERATING TEMPERATURE. recover the refrigerant from the system again.
PERSONAL INJURY MAY RESULT. Do not discharge refrigerant into the atmosphere.
• DO NOT STORE ENGINE COOLANT IN OPEN Use an R-134a refrigerant recovery/recycling device
OR UNMARKED CONTAINERS. that meets SAE Standard J2210.
• HOT ENGINE COOLANT CAN CAUSE SEVERE The refrigerant system will remain chemically sta-
BURNS. DO NOT OPEN THE RADIATOR DRAIN ble as long as pure, moisture-free R-134a refrigerant
COCK WHEN THE COOLING SYSTEM IS HOT AND and refrigerant oil is used. Dirt, moisture, or air can
PRESSURIZED. ALLOW THE COOLANT TO REACH upset this chemical stability. Operational troubles or
TO ROOM TEMPERATURE BEFORE STARTING serious damage can occur if foreign material is
REPAIR OPERATIONS. present in the refrigerant system.
When it is necessary to open the refrigerant sys-
The engine cooling system is designed to develop tem, have everything needed to service the system
internal pressures of 97 to 124 kPa (14 to 18 psi). ready. The refrigerant system should not be left open
Allow the vehicle 15 minutes to cool down, or wait to the atmosphere any longer than necessary. Cap or
until a safe temperature and pressure are attained, plug all lines and fittings as soon as they are opened
before opening the cooling system. Refer to Group 7 - to prevent the entrance of dirt and moisture. All lines
Cooling System for more information. and components in parts stock should be capped or
sealed until they are to be installed.
REFRIGERANT HOSES/LINES/TUBES
All tools, including the refrigerant recycling equip-
PRECAUTIONS
ment, the manifold gauge set, and test hoses should
Kinks or sharp bends in the refrigerant plumbing
be kept clean and dry. All tools and equipment must
will reduce the capacity of the entire system. High
be designed for R-134a refrigerant.
pressures are produced in the system when it is oper-
ating. Extreme care must be exercised to make sure
that all refrigerant system connections are pressure DESCRIPTION AND OPERATION
tight.
A good rule for the flexible hose refrigerant lines is ACCUMULATOR
to keep the radius of all bends at least ten times the The accumulator is mounted in the engine com-
diameter of the hose. Sharp bends will reduce the partment between the evaporator coil outlet tube and
flow of refrigerant. The flexible hose lines should be the compressor inlet. Refrigerant enters the accumu-
routed so they are at least 80 mm (3 inches) from the lator canister as a low pressure vapor through the
exhaust manifold. It is a good practice to inspect all inlet tube.
flexible refrigerant system hose lines at least once a Any liquid, oil-laden refrigerant falls to the bottom
year to make sure they are in good condition and of the canister, which acts as a separator. A desiccant
properly routed. bag is mounted inside the accumulator canister to
There are two types of refrigerant fittings: absorb any moisture which may have entered and
• All fittings with O-rings need to be coated with become trapped in the refrigerant system (Fig. 2).
refrigerant oil before installation. Use only O-rings
approved for use with R-134a refrigerant. Failure to BLOWER MOTOR
do so may result in a leak. The blower motor and blower wheel are located in
• Unified plumbing connections with aluminum the passenger side end of the heater-A/C housing,
gaskets cannot be serviced with O-rings. The gaskets below the glove box. The blower motor controls the
5. OIL RETURN FROM EVAPORATOR
VAPOR RETURN TER
INLET ORIFICE FIL-
ACCUMULATOR DOME
TUBE
O-RING SEAL CLUTCHPRESSUREHOLE COM-
DESICCANTFITTING
ANTI-SIPHON PRES-
SWITCH BAG
CYCLING PRESSOR
OUTLET SWITCH
SURE TO
XJ HEATING AND AIR CONDITIONING 24 - 5
DESCRIPTION AND OPERATION (Continued)
(PDC) directly to the blower motor. The relay is ener-
gized when the relay coil is provided a voltage signal
by the ignition switch. See the Diagnosis and Testing
section of this group for more information on the
operation of the blower motor relay.
The blower motor relay is located in a wire harness
connector that is secured to the heater-A/C housing
behind the glove box on the passenger side of the
vehicle, next to the heater-A/C wire harness connec-
tor in the passenger compartment.
The blower motor relay cannot be repaired and, if
faulty or damaged, it must be replaced.
BLOWER MOTOR RESISTOR
The blower motor resistor is mounted to the bot-
tom of the heater-A/C housing on the passenger side
of the vehicle under the instrument panel. It can be
accessed for service by removing the heater-A/C
housing kick cover.
The resistor has multiple resistor wires, each of
which reduce the current flow to the blower motor 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. When the highest blower speed is
selected, the blower motor switch connects the blower
motor directly to ground, bypassing the blower motor
resistor.
Fig. 2 Accumulator - Typical The blower motor resistor cannot be repaired and,
velocity of air flowing through the heater-A/C hous- if faulty, it must be replaced.
ing by spinning a squirrel cage-type blower wheel
within the housing at the selected speed. The blower BLOWER MOTOR SWITCH
motor and wheel can be removed from the engine The heater or heater-A/C blower motor is con-
compartment side of the housing without heater-A/C trolled by a four position rotary-type blower motor
housing removal. switch, mounted in the heater-A/C control panel. The
The blower motor will only operate when the igni- switch allows the selection of one of four blower
tion switch is in the On position, and the heater-A/C motor speeds, but can only be turned off by selecting
mode control switch knob is in any position, except the Off position with the heater-A/C mode control
Off. The blower motor receives a fused battery feed switch knob.
through the blower motor relay whenever the igni- The blower motor switch directs the blower motor
tion switch is in the On position. The blower motor ground path through the mode control switch to the
battery feed circuit is protected by a fuse in the blower motor resistor, or directly to ground, as
Power Distribution Center (PDC). Blower motor required to achieve the selected blower motor speed.
speed is controlled by regulating the ground path The blower motor switch cannot be repaired and, if
through the heater-A/C control blower motor switch faulty or damaged, the entire heater-A/C control
and the blower motor resistor. panel must be replaced.
The blower motor and blower motor wheel cannot
be repaired and, if faulty, they must be replaced. The COMPRESSOR
blower motor and blower wheel are serviced only as a The air conditioning system uses a Sanden
unit. SD7H15 fixed displacement compressor on all mod-
els. A label identifying the use of R-134a refrigerant
BLOWER MOTOR RELAY is located on the compressor. The purpose of the com-
The blower motor relay is a International Stan- pressor is to compress the low-pressure refrigerant
dards Organization (ISO)-type relay. The relay is a vapor from the evaporator into a high-pressure, high-
electromechanical device that switches battery cur- temperature vapor. The compressor is serviced only
rent from a fuse in the Power Distribution Center as an assembly.
6. CLUTCH SNAP RING
PLATE SHAFT SNAP RING
KEY PULLEY
CLUTCH
SHIMS COIL
24 - 6 HEATING AND AIR CONDITIONING XJ
DESCRIPTION AND OPERATION (Continued)
COMPRESSOR CLUTCH the high pressure cut-off switch. See the Diagnosis
The compressor clutch assembly consists of a sta- and Testing section of this group for more informa-
tionary electromagnetic coil, a hub bearing and pul- tion on the operation of the compressor clutch relay.
ley assembly, and a clutch plate (Fig. 3). The The compressor clutch relay is located in the Power
electromagnetic coil and pulley are retained on the Distribution Center (PDC) in the engine compart-
compressor with snap rings. The clutch plate is ment. Refer to the PDC label for relay identification
mounted on the compressor shaft and secured with a and location.
nut. The compressor clutch relay cannot be repaired
and, if faulty or damaged, it must be replaced.
CONDENSER
The condenser is located in front of the engine cool-
ing radiator. It is a heat exchanger that allows the
high-pressure refrigerant gas to give up its heat to
the air passing over the condenser fins. This causes
the refrigerant gas to condense into a high-pressure
liquid refrigerant.
The condenser cannot be repaired and, if faulty or
damaged, it must be replaced.
EVAPORATOR COIL
The evaporator coil is located in the heater-A/C
housing, under the instrument panel. Refrigerant
Fig. 3 Compressor Clutch enters the evaporator as a low-temperature, low-
pressure liquid. As air passes over the fins of the
These components provide the means to engage
evaporator, the humidity in the air condenses on the
and disengage the compressor from the engine ser-
fins, and the heat from the air is absorbed by the
pentine accessory drive belt. When the clutch coil is
refrigerant. Heat absorption causes the refrigerant to
energized, it magnetically draws the clutch into con-
become a low-pressure gas before it leaves the evap-
tact with the pulley and drives the compressor shaft.
orator.
When the coil is not energized, the pulley freewheels
The evaporator coil cannot be repaired and, if
on the clutch hub bearing, which is part of the pulley.
faulty or damaged, it must be replaced.
The compressor clutch and coil are the only serviced
parts on the compressor.
FIXED ORIFICE TUBE
The compressor clutch is controlled by several com-
The fixed orifice tube is installed in the liquid line
ponents: the heater-A/C mode control switch, the low
between the outlet tube of the condenser and the
pressure cycling clutch switch, the high pressure cut-
inlet tube of the evaporator. The fixed orifice tube is
off switch, the compressor clutch relay, and the Pow-
located in the end of the liquid line or liquid line
ertrain Control Module (PCM). The PCM may delay
jumper that connects to the condenser outlet tube.
compressor clutch engagement for up to 30 seconds.
The inlet and outlet ends of the tube have a screen
Refer to Group 14 - Fuel System for more informa-
to filter the refrigerant. O-rings on the tube body pre-
tion on the PCM controls.
vent the refrigerant from bypassing the fixed orifice.
The fixed orifice tube is used to meter the flow of liq-
COMPRESSOR CLUTCH RELAY
uid refrigerant into the evaporator coil.
The compressor clutch relay is a International
The fixed orifice tube cannot be repaired and, if
Standards Organization (ISO) micro-relay. The termi-
faulty or plugged, the liquid line or liquid line
nal designations and functions are the same as a con-
jumper containing the fixed orifice tube must be
ventional ISO relay. However, the micro-relay
replaced.
terminal orientation (footprint) is different, current
capacity is lower, and the relay case dimensions are
HEATER CORE
smaller than those of the conventional ISO relay.
The heater core is located in the heater-A/C hous-
The compressor clutch relay is a electromechanical
ing, under the instrument panel. It is a heat
device that switches battery current to the compres-
exchanger made of rows of tubes and fins. Engine
sor clutch coil when the Powertrain Control Module
coolant is circulated through heater hoses to the
(PCM) grounds the coil side of the relay. The PCM
heater core at all times. As the coolant flows through
responds to inputs from the heater-A/C mode control
switch, the low pressure cycling clutch switch, and
7. XJ HEATING AND AIR CONDITIONING 24 - 7
DESCRIPTION AND OPERATION (Continued)
the heater core, heat removed from the engine is The switch contacts open and close causing the PCM
transferred to the heater core fins and tubes. to turn the compressor clutch on and off. This regu-
Air directed through the heater core picks up the lates the system pressure and controls evaporator
heat from the heater core fins. The blend air door temperature. Controlling evaporator temperature
allows control of the heater output air temperature prevents condensate water on the evaporator fins
by controlling how much of the air flowing through from freezing and obstructing air conditioning system
the heater-A/C housing is directed through the air flow.
heater core. The blower motor speed controls the The low pressure cycling clutch switch contacts are
amount of air flowing through the heater-A/C hous- open when the suction pressure is approximately 141
ing. kPa (20.5 psi) or lower. The switch contacts will close
The heater core cannot be repaired and, if faulty or when the suction pressure rises to approximately 234
damaged, it must be replaced. to 262 kPa (34 to 38 psi) or above. Lower ambient
temperatures, below approximately -1°C (30°F) dur-
HIGH PRESSURE CUT-OFF SWITCH ing cold weather will also open the switch contacts.
The high pressure cut-off switch is located on the This is due to the pressure/temperature relationship
discharge line between the compressor and the con- of the refrigerant in the system.
denser inlet. This switch is connected in series with The low pressure cycling clutch switch is a factory-
the low pressure cycling clutch switch between calibrated unit. It cannot be adjusted or repaired
ground and the Powertrain Control Module (PCM). and, if faulty or damaged, it must be replaced.
The switch contacts open and close causing the PCM
to turn the compressor clutch on and off. This pre- REFRIGERANT
vents compressor operation when the discharge line The R-134a refrigerant used in this air condition-
pressure approaches high levels. ing system is a non-toxic, non-flammable, clear, and
The high pressure cut-off switch contacts are open colorless liquefied gas. R-134a refrigerant is not com-
when the discharge line pressure rises above 3100 to patible with R-12 refrigerant in an air conditioning
3375 kPa (450 to 490 psi). The switch contacts will system.
close when the discharge line pressure drops to 1860 Even a small amount of R-12 added to a R-134a
to 2275 kPa (270 to 330 psi). refrigerant system, will cause compressor failure,
The high pressure cut-off switch is a factory-cali- refrigerant oil sludge, or poor air conditioning system
brated unit. The switch cannot be adjusted or performance. The refrigerant system service ports
repaired and, if faulty or damaged, it must be have been designed to ensure that the system is not
replaced. accidentally filled with the wrong refrigerant (R-12).
HIGH PRESSURE RELIEF VALVE REFRIGERANT LINE
The high pressure relief valve is located on the The refrigerant lines are used to carry the refrig-
compressor. The valve is used to prevent excessive erant between the various air conditioning system
refrigerant system pressure. The valve vents the sys- components. A barrier hose design is used for the air
tem when a pressure of 3445 to 4135 kPa (500 to 600 conditioning system on this vehicle. The ends of the
psi), and above, is reached. This prevents damage to refrigerant hoses are made from lightweight alumi-
the compressor and other system components due to num, and use braze-less fittings.
condenser air flow being restricted or an overcharge Kinks or sharp bends in the refrigerant plumbing
of refrigerant. The valve closes with a minimum will reduce the capacity of the entire system. High
pressure of 2756 kPa (400 psi). pressures are produced in the system when it is oper-
The high pressure relief valve vents only enough ating. Extreme care must be exercised to make sure
refrigerant to reduce system pressure, and then that all refrigerant system connections are pressure
re-seats itself. The majority of the refrigerant is con- tight.
served in the system. If the valve vents refrigerant, it A good rule for the flexible hose refrigerant lines is
does not mean the valve is faulty. The valve is part of to keep the radius of all bends at least ten times the
the compressor assembly and must not be removed or diameter of the hose. Sharp bends will reduce the
otherwise disturbed. flow of refrigerant. The flexible hose lines should be
routed so they are at least 80 mm (3 inches) from the
LOW PRESSURE CYCLING CLUTCH SWITCH exhaust manifold. It is a good practice to inspect all
The low pressure cycling clutch switch is mounted flexible refrigerant system hose lines at least once a
on top of the accumulator. The switch is connected in year to make sure they are in good condition and
series with the high pressure cut-off switch, between properly routed.
ground and the Powertrain Control Module (PCM).
8. LOW (BLUE W/BLACK STRIP)
LOW VALVEGAUGE
PRESSURE HOSE HOSE HIGH STRIP) STRIP)
HIGHVACUUM/REFRIG- VALVE
W/BLACK HOSE GAUGE
ERANT
LOW W/BLACK (YEL-
PRESSURE
(RED
PRESSURE
24 - 8 HEATING AND AIR CONDITIONING XJ
DESCRIPTION AND OPERATION (Continued)
The refrigerant lines and hoses cannot be repaired
and, if faulty or damaged, they must be replaced.
REFRIGERANT LINE COUPLER
Spring-locking refrigerant line couplers are used to
connect refrigerant lines and other components to the
refrigerant system. The coupling is held together by
a garter spring inside a circular cage.
When the coupling halves are connected, the flared
end of the female fitting slips behind the garter
spring inside the cage of the male fitting. The garter
spring and cage prevent the flared end of the female
fitting from pulling out of the cage. Secondary clips
are installed over the coupling at the factory for
added blowoff protection.
O-rings are used to seal the coupling. These
O-rings are compatible with R-134a refrigerant and
must be replaced with O-rings made of the same
material.
REFRIGERANT OIL
The oil used in the SD7H15 compressor is a poly- Fig. 4 Manifold Gauge Set
alkylene glycol, synthetic (SP-20 PAG), wax-free
refrigerant oil. Use only refrigerant oil of the same MANIFOLD GAUGE SET CONNECTIONS
type to service the system.
CAUTION: Do not use an R-12 manifold gauge set
Refrigerant oil will absorb any moisture it comes in
on an R-134a system. The refrigerants are not com-
contact with, even moisture in the air. The oil con-
patible and system damage will result.
tainer should be kept tightly capped until it is ready
to be used. Then, cap the oil immediately after using,
to prevent contamination. LOW PRESSURE GAUGE HOSE
The low pressure hose (Blue with Black stripe)
REFRIGERANT SYSTEM SERVICE EQUIPMENT attaches to the suction service port. This port is
located on the suction line between the accumulator
WARNING: EYE PROTECTION MUST BE WORN outlet and the compressor.
WHEN SERVICING AN AIR CONDITIONING REFRIG-
ERANT SYSTEM. TURN OFF (ROTATE CLOCKWISE) HIGH PRESSURE GAUGE HOSE
ALL VALVES ON THE EQUIPMENT BEING USED, The high pressure hose (Red with Black stripe)
BEFORE CONNECTING TO OR DISCONNECTING attaches to the discharge service port. This port is
FROM THE REFRIGERANT SYSTEM. FAILURE TO located on the discharge line between the compressor
OBSERVE THESE WARNINGS MAY RESULT IN PER- and the condenser inlet.
SONAL INJURY.
RECOVERY/RECYCLING/EVACUATION/CHARGING
When servicing the air conditioning system, a HOSE
refrigerant charging station and a recovery/recycling The center manifold hose (Yellow, or White, with Black
device for R-134a must be used. This device must stripe) is used to recover, evacuate, and charge the refrig-
meet SAE Standard J2210. Contact an automotive erant system. When the low or high pressure valves on
service equipment supplier for refrigerant charging the manifold gauge set are opened, the refrigerant in the
and recycling/recovering equipment. Refer to the system will escape through this hose.
operating instructions provided with the equipment
for proper operation. REFRIGERANT SYSTEM SERVICE PORT
A manifold gauge set may be needed with some The two refrigerant system service ports are used
charging and/or recovery/recycling devices (Fig. 4). to charge, recover/recycle, evacuate, and test the air
The service hoses on the gauge set being used should conditioning refrigerant system. Unique service port
have manual (turn wheel), or automatic back-flow coupler sizes are used on the R-134a system, to
valves at the service port connector ends. This will ensure that the refrigerant system is not accidentally
prevent refrigerant from being released into the contaminated by the use of the wrong refrigerant
atmosphere. (R-12), or refrigerant system service equipment.
9. CLUTCH
PRESSURECYCLING
ACCUMULATOR
SWITCH
XJ HEATING AND AIR CONDITIONING 24 - 9
DESCRIPTION AND OPERATION (Continued)
The high pressure service port is located on the the moisture in the air that condenses on the evapo-
discharge line, between the compressor and the con- rator fins. Condensing the moisture in the air trans-
denser inlet. The low pressure service port is located fers heat energy into the evaporator fins and tubing.
on the suction line, between the accumulator outlet This reduces the amount of heat the evaporator can
and the compressor. After servicing the refrigerant absorb from the air. High humidity greatly reduces
system, always reinstall the service port caps. the ability of the evaporator to lower the temperature
of the air.
VACUUM CHECK VALVE However, evaporator capacity used to reduce the
A one-way vacuum check valve is installed in the amount of moisture in the air is not wasted. Wring-
accessory vacuum supply line near the vacuum tap ing some of the moisture out of the air entering the
on the engine intake manifold in the engine compart- vehicle adds to the comfort of the passengers.
ment. This check valve helps to maintain the system Although, an owner may expect too much from their
vacuum needed to retain the selected heater-A/C air conditioning system on humid days. A perfor-
mode settings by preventing the engine from bleed- mance test is the best way to determine whether the
ing down system vacuum through the intake mani- system is performing up to standard. This test also
fold during extended heavy engine load (low engine provides valuable clues as to the possible cause of
vacuum) operation. trouble with the air conditioning system.
The vacuum check valve cannot be repaired and, if Review the Service Warnings and Precautions in
faulty or damaged, it must be replaced. the front of this group before performing this proce-
dure. The air temperature in the test room and in
VACUUM RESERVOIR the vehicle must be a minimum of 21°C (70°F) for
The vacuum reservoir is mounted to the front this test.
bumper bar behind the passenger side bumper end (1) Connect a tachometer and a manifold gauge set.
cap. Vacuum stored in the reservoir is used to oper- (2) Set the heater-A/C mode control switch knob in
ate the vacuum-controlled vehicle accessories during the Recirculation Mode position, the temperature
periods of low engine vacuum, such as when the control knob in the full cool position, and the blower
vehicle is climbing a steep grade or under other high motor switch knob in the highest speed position.
engine load operating conditions. (3) Start the engine and hold the idle at 1,000 rpm
The vacuum reservoir cannot be repaired and, if with the compressor clutch engaged.
faulty or damaged, it must be replaced. (4) The engine should be at operating temperature.
The doors and windows must be open.
(5) Insert a thermometer in the driver side center
DIAGNOSIS AND TESTING A/C (panel) outlet. Operate the engine for five minutes.
A/C PERFORMANCE (6) The compressor clutch may cycle, depending
The air conditioning system is designed to provide upon the ambient temperature and humidity. If the
the passenger compartment with low temperature clutch cycles, unplug the low pressure cycling clutch
and low humidity air. The evaporator, located in the switch wire harness connector from the switch
heater-A/C housing on the dash panel below the located on the accumulator (Fig. 5). Place a jumper
instrument panel, is cooled to temperatures near the wire across the terminals of the low pressure cycling
freezing point. As warm damp air passes over the clutch switch wire harness connector.
fins in the evaporator, the air is cooled and the mois-
ture is removed as it condenses on the fins. During
periods of high heat and humidity, an air condition-
ing system will be more effective in the Recirculation
Mode. With the system in the Recirculation Mode,
only air from the passenger compartment passes
through the evaporator. As the passenger compart-
ment air dehumidifies, the air conditioning system
performance levels improve.
Humidity has an important bearing on the temper-
ature of the air delivered to the interior of the vehi-
cle. It is important to understand the effect that
humidity has on the performance of the air condition-
ing system. When humidity is high, the evaporator
has to perform a double duty. It must lower the air
temperature, and it must lower the temperature of
Fig. 5 Low Pressure Cycling Clutch Switch
10. 24 - 10 HEATING AND AIR CONDITIONING XJ
DIAGNOSIS AND TESTING (Continued)
(7) With the compressor clutch engaged, record the Performance Temperature and Pressure chart (Fig.
discharge air temperature and the compressor dis- 6). If the discharge air temperature is high, see
charge pressure. Refrigerant System Leaks and Refrigerant System
(8) Compare the discharge air temperature to the Charge in this group.
(9) Compare the compressor discharge pressure to
the Performance Temperature and Pressure chart. If
the compressor discharge pressure is high, see the
Pressure Diagnosis chart
Ambient 21°C 27°C 32°C 38°C 43°C
Temperature (70°F) (80°F) (90°F) (100°F) (110°F)
Air Temperature -3 to 3°C 1 to 7°C 3 to 9°C 6 to 13°C 10 to 18°C
at Center Panel
Outlet (27-38°F) (33-44°F) (37-48°F) (43-55°F) (50-64°F)
Evaporator 179-241 kPa 221-283 kPa 262-324 kPa 303-365 kPa 345-414 kPa
Inlet Pressure
at Charge Port (26-35 psi) (32-41 psi) (38-47 psi) (44-53 psi) (50-60 psi)
Compressor 1240-1655 kPa 1380-1790 kPa 1720-2070 kPa 1860-2345 kPa 2070-2690 kPa
Discharge
Pressure (180-240 psi) (200-260 psi) (250-300 psi) (270-340 psi) (300-390 psi)
Fig. 6 Performance Temperature and Pressure
11. XJ HEATING AND AIR CONDITIONING 24 - 11
DIAGNOSIS AND TESTING (Continued)
Pressure Diagnosis
Condition Possible Causes Correction
Rapid compressor clutch cycling 1. Low refrigerant system charge. 1. See Refrigerant System Leaks in
(ten or more cycles per minute). this group. Test the refrigerant
system for leaks. Repair, evacuate
and charge the refrigerant system, if
required.
Equal pressures, but the 1. No refrigerant in the refrigerant 1. See Refrigerant System Leaks in
compressor clutch does not system. this group. Test the refrigerant
engage. 2. Faulty fuse. system for leaks. Repair, evacuate
3. Faulty compressor clutch coil. and charge the refrigerant system, if
4. Faulty compressor clutch relay. required.
5. Improperly installed or faulty low 2. Check the fuses in the Power
pressure cycling clutch switch. Distribution Center and the junction
6. Faulty high pressure cut-off block. Repair the shorted circuit or
switch. component and replace the fuses, if
7. Faulty Powertrain Control Module required.
(PCM). 3. See Compressor Clutch Coil in
this group. Test the compressor
clutch coil and replace, if required.
4. See Compressor Clutch Relay in
this group. Test the compressor
clutch relay and relay circuits. Repair
the circuits or replace the relay, if
required.
5. See Low Pressure Cycling Clutch
Switch in this group. Test the low
pressure cycling clutch switch and
tighten or replace, if required.
6. See High Pressure Cut-Off Switch
in this group. Test the high pressure
cut-off switch and replace, if
required.
7. Refer to the proper Diagnostic
Procedures manual for testing of the
PCM. Test the PCM and replace, if
required.
Normal pressures, but A/C 1. Excessive refrigerant oil in 1. See Refrigerant Oil Level in this
Performance Test air temperatures system. group. Recover the refrigerant from
at center panel outlet are too high. 2. Temperature control cable the refrigerant system and inspect
improperly installed or faulty. the refrigerant oil content. Restore
3. Blend-air door inoperative or the refrigerant oil to the proper level,
sealing improperly. if required.
2. See Temperature Control Cable in
this group. Inspect the temperature
control cable for proper routing and
operation and correct, if required.
3. See Blend-Air Door under
Heater-A/C Housing Door in this
group. Inspect the blend-air door for
proper operation and sealing and
correct, if required.
12. 24 - 12 HEATING AND AIR CONDITIONING XJ
DIAGNOSIS AND TESTING (Continued)
Pressure Diagnosis
Condition Possible Causes Correction
The low side pressure is normal or 1. Low refrigerant system charge. 1. See Refrigerant System Leaks in
slightly low, and the high side 2. Refrigerant flow through the this group. Test the refrigerant
pressure is too low. accumulator is restricted. system for leaks. Repair, evacuate
3. Refrigerant flow through the and charge the refrigerant system, if
evaporator coil is restricted. required.
4. Faulty compressor. 2. See Accumulator in this group.
Replace the restricted accumulator, if
required.
3. See Evaporator Coil in this group.
Replace the restricted evaporator
coil, if required.
4. See Compressor in this group.
Replace the compressor, if required.
The low side pressure is normal or 1. Condenser air flow restricted. 1. Check the condenser for
slightly high, and the high side 2. Inoperative cooling fan. damaged fins, foreign objects
pressure is too high. 3. Refrigerant system overcharged. obstructing air flow through the
4. Air in the refrigerant system. condenser fins, and missing or
5. Engine overheating. improperly installed air seals. Refer
to Group 7 - Cooling System for
more information on air seals. Clean,
repair, or replace components as
required.
2. Refer to Group 7 - Cooling
System for more information. Test
the cooling fan and replace, if
required.
3. See Refrigerant System Charge in
this group. Recover the refrigerant
from the refrigerant system. Charge
the refrigerant system to the proper
level, if required.
4. See Refrigerant System Leaks in
this group. Test the refrigerant
system for leaks. Repair, evacuate
and charge the refrigerant system, if
required.
5. Refer to Group 7 - Cooling
System for more information. Test
the cooling system and repair, if
required.
The low side pressure is too high, 1. Accessory drive belt slipping. 1. Refer to Group 7 - Cooling
and the high side pressure is too 2. Fixed orifice tube not installed. System for more information. Inspect
low. 3. Faulty compressor. the accessory drive belt condition
and tension. Tighten or replace the
accessory drive belt, if required.
2. See Fixed Orifice Tube in this
group. Install the missing fixed orifice
tube, if required.
3. See Compressor in this group.
Replace the compressor, if required.
13. XJ HEATING AND AIR CONDITIONING 24 - 13
DIAGNOSIS AND TESTING (Continued)
Pressure Diagnosis
Condition Possible Causes Correction
The low side pressure is too low, 1. Restricted refrigerant flow through 1. See Liquid Line and Suction and
and the high side pressure is too the refrigerant lines. Discharge Line in this group. Inspect
high. 2. Restricted refrigerant flow through the refrigerant lines for kinks, tight
the fixed orifice tube. bends or improper routing. Correct
3. Restricted refrigerant flow through the routing or replace the refrigerant
the condenser. line, if required.
2. See Fixed Orifice Tube in this
group. Replace the restricted fixed
orifice tube, if required.
3. See Condenser in this group.
Replace the restricted condenser, if
required.
.
HEATER PERFORMANCE Minimum Heater
System
PREPARATIONS Ambient Temperature Floor Outlet
Review the Service Warnings and Precautions in Temperature
the front of this group before performing the follow- Celsius Fahrenheit Celsius Fahrenheit
ing procedures.
Check the radiator coolant level, serpentine drive 15.5° 60° 62.2° 144°
belt tension, and engine vacuum line connections. 21.1° 70° 63.8° 147°
Also check the radiator air flow and the radiator fan 26.6° 80° 65.5° 150°
operation. Start the engine and allow it to warm up 32.2° 90° 67.2° 153°
to normal operating temperature.
Fig. 7 Temperature Reference
WARNING: DO NOT REMOVE THE RADIATOR
PRESSURE CAP WHEN THE ENGINE IS AT OPER- return hose is much cooler than the supply hose,
ATING TEMPERATURE, PERSONAL INJURY MAY locate and repair the engine coolant flow obstruction
RESULT. in the heater system.
If the vehicle has been operated recently, wait fif- OBSTRUCTED COOLANT FLOW
teen minutes or longer before removing the radiator Possible locations or causes of obstructed coolant
pressure cap. Place a rag over the cap and turn it to flow:
the first safety stop. Allow any pressure to escape • Pinched or kinked heater hoses.
through the overflow tube. When the system stabi- • Improper heater hose routing.
lizes, remove the cap completely. • Plugged heater hoses or supply and return ports
at the cooling system connections (refer to Group 7 -
MAXIMUM HEATER OUTPUT Cooling System).
Engine coolant is delivered to the heater core • A plugged heater core.
through two heater hoses. With the engine idling at If proper coolant flow through the heater system is
normal operating temperature, set the temperature verified, and outlet air temperature is still low, a
control knob in the full hot position, the mode control mechanical problem may exist.
switch knob in the Floor position, and the blower
motor switch knob in the highest speed position. MECHANICAL PROBLEMS
Using a test thermometer, check the air temperature Possible locations or causes of insufficient heat:
coming from the floor outlets, refer to the Tempera- • An obstructed cowl air intake.
ture Reference chart (Fig. 7). • Obstructed heater system outlets.
If the floor outlet air temperature is low, refer to • A blend-air door not functioning properly.
Group 7 - Cooling System for the coolant tempera-
ture specifications. Both of the heater hoses should TEMPERATURE CONTROL
be hot to the touch. The coolant return hose should If the heater discharge air temperature cannot be
be slightly cooler than the supply hose. If the coolant adjusted with the temperature control knob on the
14. 24 - 14 HEATING AND AIR CONDITIONING XJ
DIAGNOSIS AND TESTING (Continued)
heater-A/C control panel, the following could require (2) Connect the test set vacuum supply hose to the
service: heat-A/C system side of the valve. When connected to
• The heater-A/C control. this side of the check valve, no vacuum should pass
• The temperature control cable. and the test set gauge should return to the 27 kPa (8
• The blend-air door. in. Hg.) setting. If OK, go to Step 3. If not OK,
• Improper engine coolant temperature. replace the faulty valve.
(3) Connect the test set vacuum supply hose to the
VACUUM SYSTEM engine vacuum side of the valve. When connected to
Vacuum control is used to operate the mode doors this side of the check valve, vacuum should flow
in the heater-A/C housing. Testing of the heater-A/C through the valve without restriction. If not OK,
mode control switch operation will determine if the replace the faulty valve.
vacuum, and mechanical controls are functioning.
However, it is possible that a vacuum control system HEATER-A/C CONTROLS
that operates perfectly at engine idle (high engine (1) Connect the test set vacuum probe to the heat-
vacuum) may not function properly at high engine A/C system vacuum supply (black) tube at the tee in
speeds or loads (low engine vacuum). This can be the engine compartment. Position the test set gauge
caused by leaks in the vacuum system, or a faulty so that it can be viewed from the passenger compart-
vacuum check valve. ment.
A vacuum system test will help to identify the (2) Place the heater-A/C mode control switch knob
source of poor vacuum system performance, or locate in each mode position, one at a time, and pause after
vacuum system leaks. Before starting this test, stop each selection. The test set gauge should return to
the engine and make certain that the problem isn’t a the 27 kPa (8 in. Hg.) setting shortly after each selec-
disconnected vacuum supply tube at the engine tion is made. If not OK, a component or vacuum line
intake manifold vacuum tap or the vacuum reservoir. in the vacuum circuit of the selected mode has a
Use an adjustable vacuum test set (Special Tool leak. See the procedure in Locating Vacuum Leaks.
C-3707) and a suitable vacuum pump to test the
heater-A/C vacuum control system. With a finger CAUTION: Do not use lubricant on the switch ports
placed over the end of the vacuum test hose probe or in the holes in the plug, as lubricant will ruin the
(Fig. 8), adjust the bleed valve on the test set gauge vacuum valve in the switch. A drop of clean water
to obtainBLEEDvacuum of exactly 27 kPa (8 in. Hg.).
a C-3707
VACUUM TEST SET PROBE VACUUM PUMP C-4289
VALVE TOOL in the connector plug holes will help the connector
Release and block the end of the probe several times slide onto the switch ports.
to verify that the vacuum reading returns to the
exact 27 kPa (8 in. Hg.) setting. Otherwise, a false LOCATING VACUUM LEAKS
reading will be obtained during testing.
WARNING: ON VEHICLES EQUIPPED WITH AIR-
BAGS, REFER TO GROUP 8M - PASSIVE
RESTRAINT SYSTEMS BEFORE ATTEMPTING ANY
STEERING WHEEL, STEERING COLUMN, OR
INSTRUMENT PANEL COMPONENT DIAGNOSIS OR
SERVICE. FAILURE TO TAKE THE PROPER PRE-
CAUTIONS COULD RESULT IN ACCIDENTAL AIR-
BAG DEPLOYMENT AND POSSIBLE PERSONAL
INJURY.
(1) Disconnect the vacuum harness connector
behind the glove box and inboard of the glove box
opening on the heater-A/C housing.
(2) Connect the test set vacuum hose probe to each
port in the heater-A/C housing half of the vacuum
harness connector, one at a time, and pause after
Fig. 8 Adjust Vacuum Test Bleed Valve each connection (Fig. 9). The test set gauge should
return to the 27 kPa (8 in. Hg.) setting shortly after
VACUUM CHECK VALVE each connection is made. If OK, replace the faulty
(1) Remove the vacuum check valve. The valve is heater-A/C control. If not OK, go to Step 3.
located in the (black) vacuum supply tube at the (3) Determine the vacuum line color of the vacuum
heat-A/C system vacuum tap. circuit that is leaking. To determine the vacuum line
15. XJ HEATING AND AIR CONDITIONING 24 - 15
DIAGNOSIS AND TESTING (Continued)
ing Diagrams. Possible causes of an inoperative
blower motor include:
• Faulty fuse
• Faulty blower motor circuit wiring or wire har-
ness connectors
• Faulty blower motor resistor
• Faulty blower motor relay
• Faulty blower motor switch
• Faulty heater-A/C mode control switch
• Faulty blower motor.
Possible causes of the blower motor not operating
in all speeds include:
• Faulty fuse
• Faulty blower motor switch
• Faulty blower motor resistor
• Faulty blower motor circuit wiring or wire har-
ness connectors.
VIBRATION
Fig. 9 Vacuum Circuit Test Possible causes of blower motor vibration include:
colors, refer to the Vacuum Circuits chart (Fig. 10) or • Improper blower motor mounting
(Fig. 11). • Improper blower wheel mounting
(4) Disconnect and plug the vacuum line from the • Blower wheel out of balance or bent
component (fitting, actuator, valve, switch, or reser- • Blower motor faulty.
voir) on the other end of the leaking circuit. Instru-
ment panel disassembly or removal may be necessary NOISE
to gain access to some components. See the service To verify that the blower is the source of the noise,
procedures in this group. unplug the blower motor wire harness connector and
(5) Connect the test set hose or probe to the open operate the heater-A/C system. If the noise goes
end of the leaking circuit. The test set gauge should away, possible causes include:
return to the 27 kPa (8 in. Hg.) setting shortly after • Foreign material in the heater-A/C housing
each connection is made. If OK, replace the faulty • Improper blower motor mounting
disconnected component. If not OK, go to Step 6. • Improper blower wheel mounting
(6) To locate a leak in a vacuum line, leave one • Blower motor faulty.
end of the line plugged and connect the test set hose
or probe to the other end. Run your fingers slowly BLOWER MOTOR RELAY
along the line while watching the test set gauge. The
vacuum reading will fluctuate when your fingers con- WARNING: ON VEHICLES EQUIPPED WITH AIR-
tact the source of the leak. To repair the vacuum BAGS, REFER TO GROUP 8M - PASSIVE
line, cut out the leaking section of the line. Then, RESTRAINT SYSTEMS BEFORE ATTEMPTING ANY
insert the loose ends of the line into a suitable length STEERING WHEEL, STEERING COLUMN, OR
of 3 mm (1/8-inch) inside diameter rubber hose. INSTRUMENT PANEL COMPONENT DIAGNOSIS OR
SERVICE. FAILURE TO TAKE THE PROPER PRE-
BLOWER MOTOR CAUTIONS COULD RESULT IN ACCIDENTAL AIR-
BAG DEPLOYMENT AND POSSIBLE PERSONAL
WARNING: ON VEHICLES EQUIPPED WITH AIR- INJURY.
BAGS, REFER TO GROUP 8M - PASSIVE
RESTRAINT SYSTEMS BEFORE ATTEMPTING ANY
RELAY TEST
STEERING WHEEL, STEERING COLUMN, OR
The blower motor relay is located in a wire harness
INSTRUMENT PANEL COMPONENT DIAGNOSIS OR
connector that is secured to the heater-A/C housing
SERVICE. FAILURE TO TAKE THE PROPER PRE-
behind the glove box on the passenger side of the
CAUTIONS COULD RESULT IN ACCIDENTAL AIR-
vehicle, next to the heater-A/C wire harness connec-
BAG DEPLOYMENT AND POSSIBLE PERSONAL
tor in the passenger compartment. Remove the relay
INJURY.
from its connector to perform the following tests:
For circuit descriptions and diagrams, refer to (1) A relay in the de-energized position should
8W-42 - Air Conditioning/Heater in Group 8W - Wir- have continuity between terminals 87A and 30, and
16. DEFROST
BI-LEVEL
VENTED
FLOOR
PANEL
Yellow
Brown
Black
Blue
OFF
Red
MIX VACUUM
24 - 16 HEATING AND AIR CONDITIONING XJ
DIAGNOSIS AND TESTING (Continued)
VACUUM CIRCUIT LEGEND
I.D. Function Color
A Not Used N/A
B Defrost Actuator (Full Position) Yellow
C Floor Actuator Brown
D Defrost Actuator (Mid-Position) Blue
E Vacuum Supply (Reservoir) Black
F Panel Actuator Red
G Not Used N/A
Fig. 10 Vacuum Circuits - Heater Only
17. Blue Yellow A/C-BI FLOOR
Blue Yellow
Yellow
A/C-RECIRCULATION
Black
Black
Black Brown
Green
LEVEL
Green
Green VACUUM
Red
Red VENTED Yellow Black DEFROST
Blue
Blue Black OR Brown
A/C-OUTSIDE
Yellow
Blue
Yellow Brown
PANEL
Green
Green
Green
Brown
Green
MIX
Brown
OFF Red
Red
Red
XJ HEATING AND AIR CONDITIONING 24 - 17
DIAGNOSIS AND TESTING (Continued)
VACUUM CIRCUIT LEGEND
I.D. Function Color
A Not Used N/A
B Defrost Actuator (Full Position) Yellow
C Floor Actuator Brown
D Defrost Actuator (Mid-Position) Blue
E Vacuum Supply (Reservoir) Black
F Panel Actuator Red
G Recirculation Actuator Green
Fig. 11 Vacuum Circuits - Heater-A/C
18. RELAY CAVITIES
RELAY TERMINALS
24 - 18 HEATING AND AIR CONDITIONING XJ
DIAGNOSIS AND TESTING (Continued)
no continuity between terminals 87 and 30. If OK, go OK, repair the open circuit to the junction block fuse
to Step 2. If not OK, replace the faulty relay. as required.
(2) Resistance between terminals 85 and 86 (elec- (5) The coil ground terminal cavity (85) is con-
tromagnet) should be 75 Ϯ 5 ohms. If OK, go to Step nected to ground. This terminal supplies the ground
3. If not OK, replace the faulty relay. for the relay electromagnet coil. There should be con-
(3) Connect a battery to terminals 85 and 86. tinuity between the cavity for relay terminal 85 and
There should now be continuity between terminals a good ground at all times. If not OK, repair the open
30 and 87, and no continuity between terminals 87A circuit as required.
and 30. If OK, see the Circuit Test in this group. If
not OK, replace the faulty relay. BLOWER MOTOR RESISTOR
For circuit descriptions and diagrams, refer to
8W-42 - Air Conditioning/Heater in Group 8W - Wir-
ing Diagrams.
WARNING: ON VEHICLES EQUIPPED WITH AIR-
BAGS, REFER TO GROUP 8M - PASSIVE
RESTRAINT SYSTEMS BEFORE ATTEMPTING ANY
STEERING WHEEL, STEERING COLUMN, OR
INSTRUMENT PANEL COMPONENT DIAGNOSIS OR
SERVICE. FAILURE TO TAKE THE PROPER PRE-
CAUTIONS COULD RESULT IN ACCIDENTAL AIR-
BAG DEPLOYMENT AND POSSIBLE PERSONAL
INJURY.
To test the blower motor resistor, unplug the resis-
tor wire harness connector. Each blower motor switch
input terminal on the resistor must have continuity
Blower Motor Relay to the resistor output terminal, which is connected to
CIRCUIT TEST the circuit going to the blower motor. If the blower
(1) The relay common feed terminal cavity (30) is motor resistor continuity does not check OK, replace
connected to fused battery feed directly from a fuse the faulty resistor.
in the Power Distribution Center (PDC), and should
be hot at all times. Check for battery voltage at the BLOWER MOTOR SWITCH
connector cavity for relay terminal 30. If OK, go to For circuit descriptions and diagrams, refer to
Step 2. If not OK, repair the open circuit to the PDC 8W-42 - Air Conditioning/Heater in Group 8W - Wir-
as required. ing Diagrams. The blower motor switch is only ser-
(2) The relay normally closed terminal cavity (87A) viced as a part of the heater-only or heater-A/C
is not used for this application. Go to Step 3. control assembly.
(3) The relay normally open terminal cavity (87) is (1) Turn the ignition switch to the Off position.
connected to the blower motor. When the relay is Remove the heater-A/C control from the instrument
energized, terminal 87 is connected to terminal 30 panel. Check for continuity between the ground cir-
and provides full battery current to the blower motor cuit cavity of the control wire harness connector and
feed circuit. There should be continuity between the a good ground. There should be continuity. If OK, go
connector cavity for terminal 87 and the blower to Step 2. If not OK, repair the open circuit to ground
motor relay output circuit cavity of the blower motor as required.
wire harness connector at all times. If OK, go to Step (2) With the heater-A/C control wire harness con-
4. If not OK, repair the open circuit to the blower nector unplugged, place the mode control switch knob
motor as required. in any position except the Off position. Check for con-
(4) The coil battery terminal cavity (86) is con- tinuity between the ground circuit terminal and each
nected to the ignition switch. When the ignition of the blower motor driver circuit terminals of the
switch is placed in the On position, fused ignition control as you move the blower switch to each of the
switch output is directed from a fuse in the junction four speed positions. There should be continuity at
block to the relay electromagnetic coil to energize the each driver circuit terminal in only one blower motor
relay. There should be battery voltage at the connec- switch speed position. If OK, test and repair the
tor cavity for relay terminal 86 with the ignition blower driver circuits between the control connector
switch in the On position. If OK, go to Step 5. If not and the blower motor resistor as required. If not OK,
replace the faulty heater-A/C control unit.
19. XJ HEATING AND AIR CONDITIONING 24 - 19
DIAGNOSIS AND TESTING (Continued)
COMPRESSOR (2) With the heater-A/C mode control switch in any
When investigating an air conditioning related A/C mode, and the blower motor switch in the lowest
noise, you must first know the conditions under speed position, start the engine and run it at normal
which the noise occurs. These conditions include: idle.
weather, vehicle speed, transmission in gear or neu- (3) The compressor clutch coil voltage should read
tral, engine temperature, and any other special con- within two volts of the battery voltage. If there is
ditions. voltage at the clutch coil, but the reading is not
Noises that develop during air conditioning opera- within two volts of the battery voltage, test the
tion can often be misleading. For example: What clutch coil feed circuit for excessive voltage drop and
sounds like a failed front bearing or connecting rod, repair as required. If there is no voltage reading at
may be caused by loose bolts, nuts, mounting brack- the clutch coil, use a DRB scan tool and the proper
ets, or a loose clutch assembly. Verify serpentine Diagnostic Procedures manual for testing of the com-
drive belt tension. Improper belt tension can cause a pressor clutch circuit. The following components
misleading noise when the compressor is engaged. must be checked and repaired as required before you
The noise may not occur when the compressor is dis- can complete testing of the clutch coil:
engaged. • Fuses in the junction block and the Power Dis-
Drive belts are speed sensitive. At different engine tribution Center (PDC)
speeds and depending upon belt tension, belts can • Heater-A/C mode control switch
develop noises that are mistaken for a compressor • Compressor clutch relay
noise. • High pressure cut-off switch
(1) Select a quiet area for testing. Duplicate the • Low pressure cycling clutch switch
complaint conditions as much as possible. Switch the • Powertrain Control Module (PCM).
compressor on and off several times to clearly iden- (4) The compressor clutch coil is acceptable if the
tify the compressor noise. Listen to the compressor current draw measured at the clutch coil is 2.0 to 3.9
clutch while engaged and disengaged. amperes with electrical system voltage at 11.5 to 12.5
(2) To duplicate a high-ambient temperature condi- volts. This should only be checked with the work
tion (high head pressure), restrict the air flow area temperature at 21° C (70° F). If system voltage
through the condenser. Install a manifold gauge set is more than 12.5 volts, add electrical loads by turn-
to make sure that the discharge pressure does not ing on electrical accessories until the system voltage
exceed 2070 kPa (300 psi). drops below 12.5 volts.
(3) Tighten all compressor mounting bolts, the (a) If the clutch coil current reading is 4
clutch mounting nut, the clutch coil mounting screw amperes or more, the coil is shorted and should be
or nut, and the serpentine drive belt to the correct replaced.
specifications. (b) If the clutch coil current reading is zero, the
(4) Check the refrigerant system plumbing for rub- coil is open and should be replaced.
bing or interference, which can cause unusual noises.
(5) Check the refrigerant system charge. See the COMPRESSOR CLUTCH RELAY
Charging Refrigerant System procedure in this
group. RELAY TEST
(6) Check the compressor noise as in Step 1. For circuit descriptions and diagrams, refer to
(7) If the noise still exists, loosen the compressor 8W-42 - Air Conditioning/Heater in Group 8W - Wir-
mounting bolts and tighten again. Repeat Step 1. ing Diagrams.
(8) If the noise continues, replace the compressor The compressor clutch relay is located in the Power
and repeat Step 1. Distribution Center (PDC). Refer to the PDC label for
relay identification and location. Remove the relay
COMPRESSOR CLUTCH COIL from the PDC to perform the following tests:
For circuit descriptions and diagrams, refer to (1) A relay in the de-energized position should
8W-42 - Air Conditioning/Heater in Group 8W - Wir- have continuity between terminals 87A and 30, and
ing Diagrams. The battery must be fully-charged no continuity between terminals 87 and 30. If OK, go
before performing the following tests. Refer to Group to Step 2. If not OK, replace the faulty relay.
8A - Battery for more information. (2) Resistance between terminals 85 and 86 (elec-
(1) Connect an ammeter (0 to 10 ampere scale) in tromagnet) should be 75 Ϯ 5 ohms. If OK, go to Step
series with the clutch coil terminal. Use a voltmeter 3. If not OK, replace the faulty relay.
(0 to 20 volt scale) with clip-type leads for measuring (3) Connect a battery to terminals 85 and 86.
the voltage across the battery and the compressor There should now be continuity between terminals
clutch coil. 30 and 87, and no continuity between terminals 87A
