XJ                                                                                 HEATING AND AIR CONDITIONING           ...
FLOOR/PANEL DOOR              HEATER CORE       BLEND-AIR DOOR   AIR                                                 RECIR...
XJ                                                           HEATING AND AIR CONDITIONING             24 - 3GENERAL INFORM...
24 - 4    HEATING AND AIR CONDITIONING                                                                          XJGENERAL ...
OIL RETURN FROM EVAPORATOR VAPOR RETURN TER      INLET ORIFICE FIL-       ACCUMULATOR DOME             TUBE              O...
CLUTCH SNAP RING         PLATE       SHAFT SNAP RING                           KEY         PULLEY                         ...
XJ                                                                  HEATING AND AIR CONDITIONING             24 - 7DESCRIP...
LOW (BLUE W/BLACK STRIP)                                                           LOW VALVEGAUGE                         ...
CLUTCH                                                              PRESSURECYCLING                                       ...
24 - 10   HEATING AND AIR CONDITIONING                                                                       XJDIAGNOSIS A...
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24 - 12   HEATING AND AIR CONDITIONING                                                                           XJDIAGNOS...
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24 - 14    HEATING AND AIR CONDITIONING                                                                      XJDIAGNOSIS A...
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DEFROST                 BI-LEVEL                  VENTED                   FLOOR                    PANEL                 ...
Blue Yellow A/C-BI FLOOR                   Blue Yellow                      Yellow                          A/C-RECIRCULAT...
RELAY CAVITIES                                           RELAY TERMINALS24 - 18    HEATING AND AIR CONDITIONING           ...
XJ                                                               HEATING AND AIR CONDITIONING              24 - 19DIAGNOSI...
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Exj 24

  1. 1. XJ HEATING AND AIR CONDITIONING 24 - 1 HEATING AND AIR CONDITIONING CONTENTS page pageGENERAL INFORMATION HEATER PERFORMANCE . . . . . . . . . . . . . . . . 13 HEATER AND AIR CONDITIONER CONTROL . . 2 HIGH PRESSURE CUT-OFF SWITCH . . . . . . . 20 HEATER AND AIR CONDITIONER . . . . . . . . . . . 2 LOW PRESSURE CYCLING SERVICE WARNINGS AND PRECAUTIONS . . . . 3 CLUTCH SWITCH . . . . . . . . . . . . . . . . . . . . . 20DESCRIPTION AND OPERATION REFRIGERANT SYSTEM LEAKS . . . . . . . . . . . 20 ACCUMULATOR . . . . . . . . . . . . . . . . . . . . . . . . 4 VACUUM SYSTEM . . . . . . . . . . . . . . . . . . . . . . 14 BLOWER MOTOR RELAY . . . . . . . . . . . . . . . . . 5 SERVICE PROCEDURES BLOWER MOTOR RESISTOR . . . . . . . . . . . . . . 5 REFRIGERANT OIL LEVEL . . . . . . . . . . . . . . . 21 BLOWER MOTOR SWITCH . . . . . . . . . . . . . . . . 5 REFRIGERANT RECOVERY . . . . . . . . . . . . . . 21 BLOWER MOTOR . . . . . . . . . . . . . . . . . . . . . . . 4 REFRIGERANT SYSTEM CHARGE . . . . . . . . . 21 COMPRESSOR CLUTCH RELAY . . . . . . . . . . . . 6 REFRIGERANT SYSTEM EVACUATE . . . . . . . . 21 COMPRESSOR CLUTCH . . . . . . . . . . . . . . . . . . 6 REMOVAL AND INSTALLATION COMPRESSOR . . . . . . . . . . . . . . . . . . . . . . . . . 5 ACCUMULATOR . . . . . . . . . . . . . . . .. . . . . . . 32 CONDENSER . . . . . . . . . . . . . . . . . . . . . . . . . . 6 BLOWER MOTOR RELAY . . . . . . . . .. . . . . . . 37 EVAPORATOR COIL . . . . . . . . . . . . . . . . . . . . . 6 BLOWER MOTOR RESISTOR . . . . . .. . . . . . . 38 FIXED ORIFICE TUBE . . . . . . . . . . . . . . . . . . . . 6 BLOWER MOTOR . . . . . . . . . . . . . . .. . . . . . . 35 HEATER CORE . . . . . . . . . . . . . . . . . . . . . . . . . 6 COMPRESSOR CLUTCH RELAY . . . .. . . . . . . 29 HIGH PRESSURE CUT-OFF SWITCH . . . . . . . . 7 COMPRESSOR CLUTCH . . . . . . . . . .. . . . . . . 26 HIGH PRESSURE RELIEF VALVE . . . . . . . . . . . 7 COMPRESSOR . . . . . . . . . . . . . . . . .. . . . . . . 25 LOW PRESSURE CYCLING CLUTCH SWITCH . 7 CONDENSER . . . . . . . . . . . . . . . . . . .. . . . . . . 32 REFRIGERANT LINE COUPLER . . . . . . . . . . . . 8 DUCTS AND OUTLETS . . . . . . . . . . .. . . . . . . 44 REFRIGERANT LINE . . . . . . . . . . . . . . . . . . . . . 7 EVAPORATOR COIL . . . . . . . . . . . . . .. . . . . . . 43 REFRIGERANT OIL . . . . . . . . . . . . . . . . . . . . . . 8 FIXED ORIFICE TUBE . . . . . . . . . . . .. . . . . . . 31 REFRIGERANT SYSTEM SERVICE HEATER CORE . . . . . . . . . . . . . . . . .. . . . . . . 44 EQUIPMENT . . . . . . . . . . . . . . . . . . . . . . . . . . 8 HEATER-A/C CONTROL . . . . . . . . . . .. . . . . . . 35 REFRIGERANT SYSTEM SERVICE PORT . . . . . 8 HEATER-A/C HOUSING DOOR . . . . .. . . . . . . 42 REFRIGERANT . . . . . . . . . . . . . . . . . . . . . . . . . 7 HEATER-A/C HOUSING . . . . . . . . . . .. . . . . . . 39 VACUUM CHECK VALVE . . . . . . . . . . . . . . . . . . 9 HIGH PRESSURE CUT-OFF SWITCH . . . . . . . 23 VACUUM RESERVOIR . . . . . . . . . . . . . . . . . . . . 9 KICK COVER . . . . . . . . . . . . . . . . . . .. . . . . . . 37DIAGNOSIS AND TESTING LIQUID LINE . . . . . . . . . . . . . . . . . . .. . . . . . . 29 A/C PERFORMANCE . . . . . . . . . . . . . . . . . . . . . 9 LOW PRESSURE CYCLING BLOWER MOTOR RELAY . . . . . . . . . . . . . . . . 15 CLUTCH SWITCH . . . . . . . . . . . . . . . . . . . . . 31 BLOWER MOTOR RESISTOR . . . . . . . . . . . . . 18 MODE DOOR VACUUM ACTUATOR . . . . . . . . . 38 BLOWER MOTOR SWITCH . . . . . . . . . . . . . . . 18 REFRIGERANT LINE COUPLER . . . . . . . . . . . 22 BLOWER MOTOR . . . . . . . . . . . . . . . . . . . . . . 15 SUCTION AND DISCHARGE LINE . . . . . . . . . . 23 COMPRESSOR CLUTCH COIL . . . . . . . . . . . . 19 TEMPERATURE CONTROL CABLE . . . . . . . . . 36 COMPRESSOR CLUTCH RELAY . . . . . . . . . . . 19 VACUUM CHECK VALVE . . . . . . . . . . . . . . . . . 34 COMPRESSOR . . . . . . . . . . . . . . . . . . . . . . . . 19 VACUUM RESERVOIR . . . . . . . . . . . . . . . . . . . 34
  2. 2. FLOOR/PANEL DOOR HEATER CORE BLEND-AIR DOOR AIR RECIRCULATING A/C DOOR ONLYFLOOR/DE- EVAPORATOR A/CFROST ONLY DOOR24 - 2 HEATING AND AIR CONDITIONING XJGENERAL 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 ModeA/C housing assembly (Fig. 1). The system combines with the mode control knob. This will open a vacuumair conditioning, heating, and ventilating capabilities actuated recirculating air door and recirculate the airin 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 iscoil 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 groupcowl top opening at the base of the windshield, and represent only the LHD version, the diagnostic andpasses through a plenum chamber to the heater-A/C service procedures outlined can generally besystem blower housing. Air flow velocity can then be applied to either version. Exceptions to this ruleadjusted with the blower motor speed selector switch have been clearly identified as LHD or RHD, if aon 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 otherobstructions for the heater-A/C system to receive asufficient 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 aair type systems. In a blend-air system, a blend-air combination of mechanical, electrical, and vacuumdoor controls the amount of unconditioned air (or controls. These controls provide the vehicle operatorcooled air from the evaporator on models with air with a number of setting options to help control theconditioning) is allowed to flow through, or around, climate and comfort within the vehicle. Refer to thethe 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 isthe blend-air door. This allows an almost immediate located to the right of the instrument cluster on themanual 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 blowerpanel 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. 3. XJ HEATING AND AIR CONDITIONING 24 - 3GENERAL INFORMATION (Continued)SERVICE WARNINGS AND PRECAUTIONS • Do not overcharge the refrigerant system. This will cause excessive compressor head pressureWARNING: and can cause noise and system failure. • THE AIR CONDITIONING SYSTEM CONTAINSREFRIGERANT 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. NeverREFRIGERANT OIL VAPOR OR MIST. EXPOSURE open or loosen a connection before recovering theMAY 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 aCONTACT WITH THE REFRIGERANT. IF EYE CON- replacement component until you are ready to serviceTACT 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 fittingsOCCURS, 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 fittingAREA 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 sharpTUDE IS EXTREMELY HIGH. AS A RESULT, bends that may restrict refrigerant flow. Position theANYTHING THAT COMES IN CONTACT WITH THE refrigerant lines away from exhaust system componentsREFRIGERANT 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 specifiedCONTACT 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 aPRESSURE 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 theAT ELEVATED PRESSURES. THESE MIXTURES ARE atmosphere if left uncapped. Do not open a containerPOTENTIALLY 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 immediatelyERTY 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 suppliedwith 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 systemresult. must be properly maintained. • R-12 refrigerant oil must not be mixed with The use of a bug screen is not recommended. AnyR-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 andR-134a system. Damage to the system will result. engine cooling systems.
  4. 4. 24 - 4 HEATING AND AIR CONDITIONING XJGENERAL 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. ImproperBASED COOLANT AND IS HARMFUL IF SWAL- tools or improper use of the tools can damage theLOWED OR INHALED. IF SWALLOWED, DRINK refrigerant fittings. Always use two wrenches whenTWO GLASSES OF WATER AND INDUCE VOMIT- loosening or tightening tube fittings. Use one wrenchING. IF INHALED, MOVE TO A FRESH AIR AREA. to hold one side of the connection stationary, whileSEEK 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 fromYLENE 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 andTHE 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 deviceOR 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 refrigerantCOCK WHEN THE COOLING SYSTEM IS HOT AND and refrigerant oil is used. Dirt, moisture, or air canPRESSURIZED. ALLOW THE COOLANT TO REACH upset this chemical stability. Operational troubles orTO ROOM TEMPERATURE BEFORE STARTING serious damage can occur if foreign material isREPAIR 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 systeminternal pressures of 97 to 124 kPa (14 to 18 psi). ready. The refrigerant system should not be left openAllow the vehicle 15 minutes to cool down, or wait to the atmosphere any longer than necessary. Cap oruntil a safe temperature and pressure are attained, plug all lines and fittings as soon as they are openedbefore opening the cooling system. Refer to Group 7 - to prevent the entrance of dirt and moisture. All linesCooling 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 mustwill 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 surethat all refrigerant system connections are pressure DESCRIPTION AND OPERATIONtight. A good rule for the flexible hose refrigerant lines is ACCUMULATORto 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 andflow 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 theexhaust 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 bottomyear to make sure they are in good condition and of the canister, which acts as a separator. A desiccantproperly 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-ringsapproved for use with R-134a refrigerant. Failure to BLOWER MOTORdo 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. 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 TOXJ HEATING AND AIR CONDITIONING 24 - 5DESCRIPTION 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 wheelwithin the housing at the selected speed. The blower BLOWER MOTOR SWITCHmotor 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 motorhousing 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 blowertion switch is in the On position, and the heater-A/C motor speeds, but can only be turned off by selectingmode control switch knob is in any position, except the Off position with the heater-A/C mode controlOff. 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 motortion switch is in the On position. The blower motor ground path through the mode control switch to thebattery feed circuit is protected by a fuse in the blower motor resistor, or directly to ground, asPower 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, ifthrough the heater-A/C control blower motor switch faulty or damaged, the entire heater-A/C controland the blower motor resistor. panel must be replaced. The blower motor and blower motor wheel cannotbe repaired and, if faulty, they must be replaced. The COMPRESSORblower motor and blower wheel are serviced only as a The air conditioning system uses a Sandenunit. SD7H15 fixed displacement compressor on all mod- els. A label identifying the use of R-134a refrigerantBLOWER 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 refrigerantdards 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 onlyrent from a fuse in the Power Distribution Center as an assembly.
  6. 6. CLUTCH SNAP RING PLATE SHAFT SNAP RING KEY PULLEY CLUTCH SHIMS COIL24 - 6 HEATING AND AIR CONDITIONING XJDESCRIPTION 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 Powerelectromagnetic 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 identificationmounted 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 theand disengage the compressor from the engine ser- fins, and the heat from the air is absorbed by thepentine accessory drive belt. When the clutch coil is refrigerant. Heat absorption causes the refrigerant toenergized, 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, ifon 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 servicedparts on the compressor. FIXED ORIFICE TUBE The compressor clutch is controlled by several com- The fixed orifice tube is installed in the liquid lineponents: the heater-A/C mode control switch, the low between the outlet tube of the condenser and thepressure cycling clutch switch, the high pressure cut- inlet tube of the evaporator. The fixed orifice tube isoff switch, the compressor clutch relay, and the Pow- located in the end of the liquid line or liquid lineertrain 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 screenRefer 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, ifStandards Organization (ISO) micro-relay. The termi- faulty or plugged, the liquid line or liquid linenal designations and functions are the same as a con- jumper containing the fixed orifice tube must beventional ISO relay. However, the micro-relay replaced.terminal orientation (footprint) is different, currentcapacity is lower, and the relay case dimensions are HEATER COREsmaller 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 heatdevice that switches battery current to the compres- exchanger made of rows of tubes and fins. Enginesor 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 throughresponds to inputs from the heater-A/C mode controlswitch, the low pressure cycling clutch switch, and
  7. 7. XJ HEATING AND AIR CONDITIONING 24 - 7DESCRIPTION AND OPERATION (Continued)the heater core, heat removed from the engine is The switch contacts open and close causing the PCMtransferred 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 evaporatorheat from the heater core fins. The blend air door temperature. Controlling evaporator temperatureallows control of the heater output air temperature prevents condensate water on the evaporator finsby controlling how much of the air flowing through from freezing and obstructing air conditioning systemthe 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 areamount of air flowing through the heater-A/C hous- open when the suction pressure is approximately 141ing. 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 234damaged, 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 relationshipdischarge 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 repairedground and the Powertrain Control Module (PCM). and, if faulty or damaged, it must be replaced.The switch contacts open and close causing the PCMto turn the compressor clutch on and off. This pre- REFRIGERANTvents 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 conditioning3375 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-134ato 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 systembrated unit. The switch cannot be adjusted or performance. The refrigerant system service portsrepaired and, if faulty or damaged, it must be have been designed to ensure that the system is notreplaced. 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 systemrefrigerant system pressure. The valve vents the sys- components. A barrier hose design is used for the airtem when a pressure of 3445 to 4135 kPa (500 to 600 conditioning system on this vehicle. The ends of thepsi), 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 plumbingof refrigerant. The valve closes with a minimum will reduce the capacity of the entire system. Highpressure 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 surerefrigerant to reduce system pressure, and then that all refrigerant system connections are pressurere-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 isdoes not mean the valve is faulty. The valve is part of to keep the radius of all bends at least ten times thethe compressor assembly and must not be removed or diameter of the hose. Sharp bends will reduce theotherwise disturbed. flow of refrigerant. The flexible hose lines should be routed so they are at least 80 mm (3 inches) from theLOW 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 aon top of the accumulator. The switch is connected in year to make sure they are in good condition andseries with the high pressure cut-off switch, between properly routed.ground and the Powertrain Control Module (PCM).
  8. 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 PRESSURE24 - 8 HEATING AND AIR CONDITIONING XJDESCRIPTION AND OPERATION (Continued) The refrigerant lines and hoses cannot be repairedand, if faulty or damaged, they must be replaced.REFRIGERANT LINE COUPLER Spring-locking refrigerant line couplers are used toconnect refrigerant lines and other components to therefrigerant system. The coupling is held together bya garter spring inside a circular cage. When the coupling halves are connected, the flaredend of the female fitting slips behind the garterspring inside the cage of the male fitting. The garterspring and cage prevent the flared end of the femalefitting from pulling out of the cage. Secondary clipsare installed over the coupling at the factory foradded blowoff protection. O-rings are used to seal the coupling. TheseO-rings are compatible with R-134a refrigerant andmust be replaced with O-rings made of the samematerial.REFRIGERANT OIL The oil used in the SD7H15 compressor is a poly- Fig. 4 Manifold Gauge Setalkylene glycol, synthetic (SP-20 PAG), wax-freerefrigerant oil. Use only refrigerant oil of the same MANIFOLD GAUGE SET CONNECTIONStype 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 readyto 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 accumulatorWARNING: EYE PROTECTION MUST BE WORN outlet and the compressor.WHEN SERVICING AN AIR CONDITIONING REFRIG-ERANT SYSTEM. TURN OFF (ROTATE CLOCKWISE) HIGH PRESSURE GAUGE HOSEALL 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 isFROM THE REFRIGERANT SYSTEM. FAILURE TO located on the discharge line between the compressorOBSERVE THESE WARNINGS MAY RESULT IN PER- and the condenser inlet.SONAL INJURY. RECOVERY/RECYCLING/EVACUATION/CHARGING When servicing the air conditioning system, a HOSErefrigerant charging station and a recovery/recycling The center manifold hose (Yellow, or White, with Blackdevice 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 onservice equipment supplier for refrigerant charging the manifold gauge set are opened, the refrigerant in theand recycling/recovering equipment. Refer to the system will escape through this hose.operating instructions provided with the equipmentfor proper operation. REFRIGERANT SYSTEM SERVICE PORT A manifold gauge set may be needed with some The two refrigerant system service ports are usedcharging and/or recovery/recycling devices (Fig. 4). to charge, recover/recycle, evacuate, and test the airThe service hoses on the gauge set being used should conditioning refrigerant system. Unique service porthave manual (turn wheel), or automatic back-flow coupler sizes are used on the R-134a system, tovalves at the service port connector ends. This will ensure that the refrigerant system is not accidentallyprevent refrigerant from being released into the contaminated by the use of the wrong refrigerantatmosphere. (R-12), or refrigerant system service equipment.
  9. 9. CLUTCH PRESSURECYCLING ACCUMULATOR SWITCHXJ HEATING AND AIR CONDITIONING 24 - 9DESCRIPTION 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 canand the compressor. After servicing the refrigerant absorb from the air. High humidity greatly reducessystem, 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 theon 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 theirvacuum 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 theing down system vacuum through the intake mani- system is performing up to standard. This test alsofold during extended heavy engine load (low engine provides valuable clues as to the possible cause ofvacuum) operation. trouble with the air conditioning system. The vacuum check valve cannot be repaired and, if Review the Service Warnings and Precautions infaulty or damaged, it must be replaced. the front of this group before performing this proce- dure. The air temperature in the test room and inVACUUM 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 inate the vacuum-controlled vehicle accessories during the Recirculation Mode position, the temperatureperiods of low engine vacuum, such as when the control knob in the full cool position, and the blowervehicle 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 centerDIAGNOSIS 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 thethe passenger compartment with low temperature clutch cycles, unplug the low pressure cycling clutchand low humidity air. The evaporator, located in the switch wire harness connector from the switchheater-A/C housing on the dash panel below the located on the accumulator (Fig. 5). Place a jumperinstrument panel, is cooled to temperatures near the wire across the terminals of the low pressure cyclingfreezing 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. Duringperiods of high heat and humidity, an air condition-ing system will be more effective in the RecirculationMode. With the system in the Recirculation Mode,only air from the passenger compartment passesthrough the evaporator. As the passenger compart-ment air dehumidifies, the air conditioning systemperformance 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 thathumidity has on the performance of the air condition-ing system. When humidity is high, the evaporatorhas to perform a double duty. It must lower the airtemperature, and it must lower the temperature of Fig. 5 Low Pressure Cycling Clutch Switch
  10. 10. 24 - 10 HEATING AND AIR CONDITIONING XJDIAGNOSIS 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, seecharge 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 chartAmbient 21°C 27°C 32°C 38°C 43°CTemperature (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°Cat Center PanelOutlet (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 kPaInlet Pressureat 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 kPaDischargePressure (180-240 psi) (200-260 psi) (250-300 psi) (270-340 psi) (300-390 psi) Fig. 6 Performance Temperature and Pressure
  11. 11. XJ HEATING AND AIR CONDITIONING 24 - 11DIAGNOSIS AND TESTING (Continued) Pressure Diagnosis Condition Possible Causes CorrectionRapid 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 incompressor clutch does not system. this group. Test the refrigerantengage. 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 thisPerformance Test air temperatures system. group. Recover the refrigerant fromat 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. 12. 24 - 12 HEATING AND AIR CONDITIONING XJDIAGNOSIS AND TESTING (Continued) Pressure Diagnosis Condition Possible Causes CorrectionThe low side pressure is normal or 1. Low refrigerant system charge. 1. See Refrigerant System Leaks inslightly low, and the high side 2. Refrigerant flow through the this group. Test the refrigerantpressure 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 forslightly high, and the high side 2. Inoperative cooling fan. damaged fins, foreign objectspressure 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 - Coolingand the high side pressure is too 2. Fixed orifice tube not installed. System for more information. Inspectlow. 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. 13. XJ HEATING AND AIR CONDITIONING 24 - 13DIAGNOSIS 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 SystemPREPARATIONS Ambient Temperature Floor Outlet Review the Service Warnings and Precautions in Temperaturethe front of this group before performing the follow- Celsius Fahrenheit Celsius Fahrenheiting 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 ReferenceWARNING: DO NOT REMOVE THE RADIATORPRESSURE 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 obstructionRESULT. in the heater system. If the vehicle has been operated recently, wait fif- OBSTRUCTED COOLANT FLOWteen minutes or longer before removing the radiator Possible locations or causes of obstructed coolantpressure 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 isnormal operating temperature, set the temperature verified, and outlet air temperature is still low, acontrol knob in the full hot position, the mode control mechanical problem may exist.switch knob in the Floor position, and the blowermotor switch knob in the highest speed position. MECHANICAL PROBLEMSUsing 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 CONTROLbe hot to the touch. The coolant return hose should If the heater discharge air temperature cannot bebe slightly cooler than the supply hose. If the coolant adjusted with the temperature control knob on the
  14. 14. 24 - 14 HEATING AND AIR CONDITIONING XJDIAGNOSIS AND TESTING (Continued)heater-A/C control panel, the following could require (2) Connect the test set vacuum supply hose to theservice: 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 theVACUUM 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 flowin 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 CONTROLSthat 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 inspeeds or loads (low engine vacuum). This can be the engine compartment. Position the test set gaugecaused 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 knobsource of poor vacuum system performance, or locate in each mode position, one at a time, and pause aftervacuum system leaks. Before starting this test, stop each selection. The test set gauge should return tothe 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 lineintake 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 theheater-A/C vacuum control system. With a finger CAUTION: Do not use lubricant on the switch portsplaced 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 waterto 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 connectorRelease and block the end of the probe several times slide onto the switch ports.to verify that the vacuum reading returns to theexact 27 kPa (8 in. Hg.) setting. Otherwise, a false LOCATING VACUUM LEAKSreading 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 afterVACUUM 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 vacuumheat-A/C system vacuum tap. circuit that is leaking. To determine the vacuum line
  15. 15. XJ HEATING AND AIR CONDITIONING 24 - 15DIAGNOSIS 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 bentcomponent (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 NOISEto 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 goesend 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 housingeach connection is made. If OK, replace the faulty • Improper blower motor mountingdisconnected 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 hoseor probe to the other end. Run your fingers slowly BLOWER MOTOR RELAYalong the line while watching the test set gauge. Thevacuum 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 - PASSIVEline, cut out the leaking section of the line. Then, RESTRAINT SYSTEMS BEFORE ATTEMPTING ANYinsert the loose ends of the line into a suitable length STEERING WHEEL, STEERING COLUMN, ORof 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 PERSONALWARNING: ON VEHICLES EQUIPPED WITH AIR- INJURY.BAGS, REFER TO GROUP 8M - PASSIVERESTRAINT SYSTEMS BEFORE ATTEMPTING ANY RELAY TESTSTEERING WHEEL, STEERING COLUMN, OR The blower motor relay is located in a wire harnessINSTRUMENT PANEL COMPONENT DIAGNOSIS OR connector that is secured to the heater-A/C housingSERVICE. FAILURE TO TAKE THE PROPER PRE- behind the glove box on the passenger side of theCAUTIONS 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 relayINJURY. from its connector to perform the following tests: For circuit descriptions and diagrams, refer to (1) A relay in the de-energized position should8W-42 - Air Conditioning/Heater in Group 8W - Wir- have continuity between terminals 87A and 30, and
  16. 16. DEFROST BI-LEVEL VENTED FLOOR PANEL Yellow Brown Black Blue OFF Red MIX VACUUM24 - 16 HEATING AND AIR CONDITIONING XJDIAGNOSIS 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. 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 RedXJ HEATING AND AIR CONDITIONING 24 - 17DIAGNOSIS 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. 18. RELAY CAVITIES RELAY TERMINALS24 - 18 HEATING AND AIR CONDITIONING XJDIAGNOSIS AND TESTING (Continued)no continuity between terminals 87 and 30. If OK, go OK, repair the open circuit to the junction block fuseto 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 ground3. 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 andThere should now be continuity between terminals a good ground at all times. If not OK, repair the open30 and 87, and no continuity between terminals 87A circuit as required.and 30. If OK, see the Circuit Test in this group. Ifnot 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 toCIRCUIT 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, replaceconnected to fused battery feed directly from a fuse the faulty resistor.in the Power Distribution Center (PDC), and shouldbe hot at all times. Check for battery voltage at the BLOWER MOTOR SWITCHconnector cavity for relay terminal 30. If OK, go to For circuit descriptions and diagrams, refer toStep 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/Cis 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 instrumentenergized, 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 andfeed circuit. There should be continuity between the a good ground. There should be continuity. If OK, goconnector cavity for terminal 87 and the blower to Step 2. If not OK, repair the open circuit to groundmotor 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 knobmotor 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 eachnected to the ignition switch. When the ignition of the blower motor driver circuit terminals of theswitch is placed in the On position, fused ignition control as you move the blower switch to each of theswitch output is directed from a fuse in the junction four speed positions. There should be continuity atblock to the relay electromagnetic coil to energize the each driver circuit terminal in only one blower motorrelay. There should be battery voltage at the connec- switch speed position. If OK, test and repair thetor cavity for relay terminal 86 with the ignition blower driver circuits between the control connectorswitch 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. 19. XJ HEATING AND AIR CONDITIONING 24 - 19DIAGNOSIS 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 lowestnoise, you must first know the conditions under speed position, start the engine and run it at normalwhich the noise occurs. These conditions include: idle.weather, vehicle speed, transmission in gear or neu- (3) The compressor clutch coil voltage should readtral, engine temperature, and any other special con- within two volts of the battery voltage. If there isditions. 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 thetion can often be misleading. For example: What clutch coil feed circuit for excessive voltage drop andsounds like a failed front bearing or connecting rod, repair as required. If there is no voltage reading atmay be caused by loose bolts, nuts, mounting brack- the clutch coil, use a DRB scan tool and the properets, 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 componentsmisleading noise when the compressor is engaged. must be checked and repaired as required before youThe 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 switchdevelop noises that are mistaken for a compressor • Compressor clutch relaynoise. • High pressure cut-off switch (1) Select a quiet area for testing. Duplicate the • Low pressure cycling clutch switchcomplaint 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 thetify the compressor noise. Listen to the compressor current draw measured at the clutch coil is 2.0 to 3.9clutch 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 worktion (high head pressure), restrict the air flow area temperature at 21° C (70° F). If system voltagethrough 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 voltageexceed 2070 kPa (300 psi). drops below 12.5 volts. (3) Tighten all compressor mounting bolts, the (a) If the clutch coil current reading is 4clutch mounting nut, the clutch coil mounting screw amperes or more, the coil is shorted and should beor 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 RELAYCharging Refrigerant System procedure in thisgroup. 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 Powerand repeat Step 1. Distribution Center (PDC). Refer to the PDC label for relay identification and location. Remove the relayCOMPRESSOR 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 should8W-42 - Air Conditioning/Heater in Group 8W - Wir- have continuity between terminals 87A and 30, anding Diagrams. The battery must be fully-charged no continuity between terminals 87 and 30. If OK, gobefore 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 Stepseries 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 terminalsclutch coil. 30 and 87, and no continuity between terminals 87A

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