General Information

INTRODUCTION
System = R134 w/expansion valve
The heater/air conditioning systems share many of tile same components. This deals with both systems together when component function is common, and separately when they are not.

For proper operation of the instrument panel controls, refer to the Owner's Manual provided with the vehicle.

All vehicles are equipped with a common Heater A/C unit housing assembly.

OPERATION
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.

CAUTION: The system must be completely empty before opening any fitting or connection in the refrigeration system. Open fittings with caution even after the system has been emptied. If any pressure is noticed as a fitting is loosened, retighten fitting and evacuate the system again.

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.

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

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

When opening a refrigeration system, have everything you will need to repair the system ready. This will minimize the amount of time the system must be opened. Cap or plug all lines and fittings as soon as they are opened. This will help prevent the entrance of dirt and moisture. All new lines and components 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.

System Airflow
The system draws outside air through the cowl opening at the base of the windshield. Then it goes into the plenum chamber above the Heater A/C unit housing and passes through the evaporator. At this point airflow 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 control head. After the air passes the blend air door, the air flow is then 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 control head.

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 rotating the RECIRC. knob on the control head. Rotating the MODE control knob to the Defrost/Floor or Defrost setting on the control head will engage the compressor. This will send refrigerant through the evaporator, and remove heat and humidity from the air before it goes through the heater core. The compressor can also be engaged by depressing the A/C button on the control head.

Manual A/C (HVAC)
The body control module controls the mode door position by receiving different voltage levels from the HVAC control over the HVAC mode sense circuit. Included in this signal is the input for the rear window defogger. In this system, the body control module has no control of the blower motor or the passenger compartment temperature.

Synchronization of Rolling Code
Pressing any button twice on the transmitter will cause it to re-synchronize.

Engine Cooling System Requirement
The use of a bug screen is not recommended. Any obstructions forward of the condenser can reduce the effectiveness of the air conditioning system.

Air Conditioning Components
A/C Pressure Transducer
The switch is located on the discharge line near the compressor. The pressure transducer functions as the refrigerant system pressure sensor. It supports the condenser/radiator fans and compressor functions.

Clutch, Pulley And Coil
They are mounted on the compressor providing a way to drive the compressor. The compressor clutch and coil are the only serviced parts on the compressor. When the compressor is not in operation, the pulley free wheels on the clutch hub bearing. When the coil is energized the clutch plate is magnetically engaged with the pulley and turns the compressor shaft.

Compressor
The compressor compresses the low pressure refrigerant vapor from the evaporator into a high pressure, high temperature vapor. The Scroll TRS-90 Compressor is used on all models. The system uses polyalkylene glycol synthetic wax-free refrigerant oil SP-15 PAG.

Condenser
It is located in front of the engine cooling radiator. Its function is to cool the hot high pressure refrigerant gas. This causes it to condense into a high pressure liquid refrigerant.

Evaporator Coil
The coil removes heat and dehumidifies the air before it enters the vehicle. The coil is located in the A/C housing.

Evaporator Probe
The evaporator temperature probe prevents condensate water on the evaporator coil from freezing and obstructing A/C system air flow. It does this by cycling the compressor clutch on and off. The switch is attached to the evaporator coil with the sensing probe inserted into the coil fins.

Expansion Valve
The valve is used to meter refrigerant into the evaporator in accordance with cooling requirements. The valve is located in front of the evaporator coil.

High Pressure Relief Valve
The valve is located at the rear of the compressor. The valve is used to prevent excessive high system pressure. The valve vents the system when a pressure of 3445-4135 kPa (500-600 psi) and above is reached. This prevents damage to the compressor and other system components. The valve closes with a minimum pressure of 2756 kPa (400 psi).

Filter/Drier
The drier is used to remove any traces of moisture from the refrigerant system. The filter is used to separate any foreign particles.

Refrigerant Lines
The lines are used to carry the refrigerant between the various system components.

Service Gauge Port
The high pressure gauge port is located on the compressor discharge line. The low pressure gauge port is located on the suction line.

Thermal Limiter Switch
The switch is used to measure compressor surface temperature. If compressor surface temperature is excessive the switch will cut battery feed voltage to the compressor clutch. The switch will then reset once compressor surface temperature returns to normal.