Файл: 92FWD_24.pdf

Fig. 2 Fixed Displacement CompressorÐModel

TR105

Fig. 3 Variable Displacement CompressorÐModel

6C17

SYSTEM AIRFLOW

The system pulls outside (ambient) air through the cowl opening at the base of the windshield. Then it goes into the plenum chamber above the A/C-heater unit housing. On air-conditioned vehicles, the air passes through the evaporator. Air flow can be directed either through or around the heater core. This is done by adjusting the blend-air door with the TEMP control on the instrument panel. The air flow

Fig. 4 Common Blend-Air Heater A/C System

can then be directed from the PANEL, BI-LEVEL (panel and floor), and FLOOR-DEFROST outlets. Air flow velocity can be adjusted with the blower speed selector switch on the instrument panel (Fig. 5).

Fig. 5 Heater only or HeaterÐA/C Controls

On air-conditioned vehicles, ambient air intake can be shut off by closing the recirculating air door. This will recirculate the air that is already inside the vehicle. This is done by moving the TEMP control into the RECIRC position. Depressing the DEFROST or A/C button will engage the compressor. This will send refrigerant through the evaporator, and will remove heat and humidity from the air before it is directed through or around the heater core.

SIDE WINDOW DEMISTERS

The side window demisters direct air from the heater assembly. The outlets are located on the top outboard corners of the instrument panel. The Demisters operate when the A/C control mode selector is on FLOOR or DEFROST setting.

ENGINE COOLING SYSTEM REQUIREMENTS

To maintain the performance level of the heating/ air-conditioning system, the engine cooling system must be prepared as shown in this manual.

Ä

The use of a bug screen is not recommended. Any obstructions in front of the radiator or condenser can reduce the performance of the A/C or engine cooling system.

SAFETY PRECAUTIONS AND WARNINGS

WARNING: WEAR EYE PROTECTION WHEN SERVICING THE AIR-CONDITIONING REFRIGERANT SYSTEM. SERIOUS EYE INJURY CAN RESULT FROM EYE CONTACT WITH REFRIGERANT. IF EYE CONTACT IS MADE, SEEK MEDICAL ATTENTION IMMEDIATELY.

DO NOT EXPOSE REFRIGERANT TO OPEN FLAME. POISONOUS GAS IS CREATED WHEN REFRIGERANT IS BURNED. AN ELECTRONIC TYPE LEAK DETECTOR IS RECOMMENDED.

LARGE AMOUNTS OF REFRIGERANT RELEASED IN A CLOSED WORK AREA WILL DISPLACE THE OXYGEN AND CAUSE SUFFOCATION.

THE EVAPORATION RATE OF (R-12) REFRIGERANT AT AVERAGE TEMPERATURE AND ALTITUDE IS EXTREMELY HIGH. AS A RESULT, ANYTHING THAT COMES IN CONTACT WITH THE REFRIGERANT WILL FREEZE. ALWAYS PROTECT SKIN OR DELICATE OBJECTS FROM DIRECT CONTACT WITH REFRIGERANT.

CAUTION: Liquid refrigerant is corrosive to metal surfaces. Follow the operating instructions supplied with equipment being used.

COOLING SYSTEM PRECAUTIONS

WARNING: ANTIFREEZE IS AN ETHYLENE GLYCOL BASE COOLANT AND IS HARMFUL IF SWALLOWED OR INHALED. IF SWALLOWED, DRINK TWO GLASSES OF WATER AND INDUCE VOMITING. IF INHALED, MOVE TO FRESH AIR AREA. SEEK MEDICAL ATTENTION IMMEDIATELY.

DO NOT STORE IN OPEN OR UNMARKED CONTAINERS.

WASH SKIN AND CLOTHING THOROUGHLY AFTER COMING IN CONTACT WITH ETHYLENE GLYCOL.

KEEP OUT OF REACH OF CHILDREN AND PETS. DO NOT OPEN A COOLING SYSTEM WHEN THE ENGINE IS AT RUNNING TEMPERATURE. PER-

SONAL INJURY CAN RESULT.

The engine cooling system is designed to develop internal pressure of 97 to 123 kPa (14 to 18 psi). Allow the vehicle 15 minutes (or until a safe tempera-

HEATING AND AIR CONDITIONING 24 - 3

ture and pressure are attained) before opening the cooling system. Refer to Group 7, Cooling System.

HANDLING TUBING AND FITTINGS

Kinks in the refrigerant tubing or sharp bends in the refrigerant hose lines will greatly reduce the capacity of the entire system. High pressures are produced in the system when it is operating. Extreme care must be exercised to make sure that all connections are pressure tight. Dirt and moisture can enter the system when it is opened for repair or replacement of lines or components. The refrigerant oil will absorb moisture readily out of the air. This moisture will convert into acids within a closed system.

The following precautions must be observed:

The system must be completely discharged before opening any fitting or connection in the refrigeration system. Open fittings with caution even after the system has been discharged. If any pressure is noticed as a fitting is loosened, allow trapped pressure to bleed off very slowly.

A good rule for the flexible hose lines is to keep the radius of all bends at least 10 times the diameter of the hose. Sharper bends will reduce the flow of refrigerant. The flexible hose lines should be routed so they are at least 3 inches (80 mm) from the exhaust manifold. Inspect all flexible hose lines to make sure they are in good condition and properly routed.

Unified plumbing connections with aluminum gaskets cannot be serviced with O-rings. These gaskets are not reusable and do not require lubrication before installing.

The use of correct wrenches when making connections is very important. Improper wrenches or improper use of wrenches can damage the fittings.

The A/C system will remain chemical stabile as long as pure-moisture-free R-12 and refrigerant oil is used. Abnormal amounts of dirt, moisture or air can upset the chemical stability. This condition could cause operational troubles or even serious damage if present in more than very small quantities.

When it is necessary to open the refrigeration system, have everything needed to service the system ready. The system should not be left open any longer than necessary. Cap or plug all lines and fittings as soon as they are opened to prevent the entrance or dirt and moisture. All lines and components in parts stock should be capped or sealed until they are ready to be used.

All tools, including the refrigerant dispensing manifold, the manifold gauge set, and test hoses should be kept clean and dry.

GENERAL INFORMATION

The Variable Displacement Compressor (VDC) provides maximum A/C performance under most conditions. It is designed to operate continuously without any cycling of the compressor clutch. The compressor has a variable angle wobble plate with six axially oriented cylinders.

During vehicle A/C system operation, the compressor will change its displacement to match the vehicles A/C cooling demands. When the A/C system needs more cooling capacity, the compressor will increase its pumping capacity. This is done by increasing the wobble plate angle to increase the piston stroke. When the A/C system cooling demand is low, the compressor will decrease its pumping capacity by reducing the piston pumping stroke. The low cooling capacity will prevent evaporator from freezing.

COMPRESSOR IDENTIFICATION

The Variable Displacement Compressor can be identified by the location of the high pressure line. It is mounted to the end of the compressor case (Fig. 1).

VARIABLE DISPLACEMENT COMPRESSOR DIAGNOSIS

(1)Verify that refrigerant system is at full charge. Refer to the Refrigerant Service Procedures section in this Group.

(2)Perform A/C Performance Test. Refer to Heater and A/C Performance Test section in this Group.

(3)If performance is not acceptable, perform expansion valve tests. Refer to Expansion Valve Tests in this section.

(4)If expansion valve test is correct, refer to the Variable Displacement Compressor test charts.

COMPRESSOR NOISE

Excessive noise that occurs when the airconditioning is being used, can be caused by:

²Loose bolts

²Mounting brackets

²Loose clutch

²Excessive high refrigerant system operating pressure

Fig. 1 Variable Displacement CompressorÐModel

6C17

Verify compressor drive belt condition, proper refrigerant charge and head pressure before compressor repair is performed.

For noise diagnostic procedures, refer to the Compressor Noise and Compressor Clutch Diagnosis chart in this section.

COMPRESSOR CLUTCH INOPERATIVE

The air-conditioning compressor clutch electrical circuit is controlled by the engine controller. The controller is located in the engine compartment outboard of the battery.

If the compressor clutch does not engage:

Verify refrigerant charge. Refer to Refrigerant Service Procedures in this section.

If the compressor clutch still does not engage: Check for battery voltage at the differential pres-

sure cut-off switch located on the expansion valve. If voltage is not detected, refer to:

(1) Group 8W, Wiring Diagrams.