Part 2B

A/C CONDENSER
The condenser is located in the air flow in front of the engine cooling radiator. The condenser is a heat exchanger that allows the high-pressure refrigerant gas being discharged by the compressor to give up its heat to the air passing over the condenser fins.

When the refrigerant gas gives up its heat, it condenses. When the refrigerant leaves the condenser, it has become a high-pressure liquid refrigerant. The volume of air flowing over the condenser fins is critical to the proper cooling performance of the air conditioning system. Therefore, it is important that there are no objects placed in front of the radiator grille openings in the front of the vehicle or foreign material on the condenser fins that might obstruct proper air flow. Also, any factory-installed air seals or shrouds must be properly reinstalled following radiator or condenser service.

The condenser cannot be repaired and, if faulty or damaged, it must be replaced.

A/C EVAPORATOR
Front Only
The evaporator coil is located in the heater-A/C housing, on the right side of the engine compartment. The evaporator coil is positioned in the heater- A/C housing so that all air that enters the housing must pass over the fins of the evaporator before it is distributed through the system ducts and outlets. However, air passing over the evaporator coil fins will only be conditioned when the compressor is engaged and circulating refrigerant through the evaporator coil tubes.

Refrigerant enters the evaporator from the expansion valve as a low-temperature, low-pressure mixture of liquid and gas. As air flows over the fins of the evaporator, the humidity in the air condenses on the fins, and the heat from the air is absorbed by the refrigerant. Heat absorption causes the refrigerant to boil and vaporize. The refrigerant becomes a low-pressure gas before it leaves the evaporator.

The evaporator coil cannot be repaired and, if faulty or damaged, it must be replaced.

Rear

The evaporator coil for the optional rear heater-A/C unit is integral with the rear heating system heater core. This unit is referred to as the combination coil.

The combination coil functions as both the rear heater core and the rear evaporator coil.

Front
The front "H" valve-type Thermal Expansion Valve (TXV) is located at the front of the heater-A/C housing between the liquid and suction lines and the evaporator coil. High-pressure, high temperature liquid refrigerant from the liquid line passes through the expansion valve orifice, converting it into a low-pressure, low-temperature mixture of liquid and gas before it enters the evaporator coil.

A temperature sensor in the expansion valve control head monitors the temperature of the refrigerant leaving the evaporator coil through the suction line, and adjusts the orifice size at the liquid line to let the proper amount of refrigerant into the evaporator coil to meet the vehicle cooling requirements. Controlling the refrigerant flow through the evaporator ensures that none of the refrigerant leaving the evaporator is still in a liquid state, which could damage the compressor.

The expansion valve is a factory calibrated unit and cannot be adjusted or repaired. If faulty or damaged, the expansion valve must be replaced.

Rear
Models equipped with the optional rear heater-A/C unit have a second "H" valve-type thermal expansion valve (TXV) installed between the rear unit liquid and suction lines, and the combination coil. High-pressure, high temperature liquid refrigerant from the liquid line passes through the expansion valve orifice, converting it into a low-pressure, low-temperature mixture of liquid and gas before it enters the combination coil.

A temperature sensor in the expansion valve control head monitors the temperature of the refrigerant leaving the combination coil through the suction line, and adjusts the orifice size at the liquid line to let the proper amount of refrigerant into the combination coil to meet the vehicle cooling requirements. Controlling the refrigerant flow through the combination coil ensures that none of the refrigerant leaving the combination coil is still in a liquid state, which could damage the compressor.

The rear expansion valve is a factory calibrated unit and cannot be adjusted or repaired. If faulty or damaged, the expansion valve must be replaced.

HEATER CORE
Front
The heater core is located in the heater-A/C housing, on the right side of the engine compartment. It is a heat exchanger made of rows of tubes and spacers. Engine coolant is circulated through heater hoses to the heater core whenever the front water valve is open. As the coolant flows through the heater core, heat removed from the engine is transferred to the heater core spacers and tubes.

Air directed through the heater core picks up the heat from the heater core spacers. The blend air door allows control of the heater output air temperature by controlling how much of the air flowing through the heater-A/C housing is directed through or around the heater core. The blower motor speed controls the volume of air flowing through the heater-A/C system.

The heater core cannot be repaired and, if faulty or damaged, it must be replaced.

Rear
Models equipped with the optional rear heater-A/C unit have a combination coil located within the rear unit housing.

The combination coil functions as both the rear heater core and the rear evaporator coil.

COMBINATION COIL
Models equipped with the optional rear heater-A/C unit have a combination coil located within the rear unit housing. It is called a combination coil because it combines the functions of a heater core and an evaporator coil into a single heat exchanger unit.

The combination coil features six rows of tube and fin construction. The two rows located toward the outboard side of the vehicle serve as the heater core and have engine coolant circulated through them whenever the rear water valve is open. The four rows toward the inboard side of the vehicle serve as the evaporator and have refrigerant circulated through them whenever the air conditioning compressor is operating. The amount of refrigerant flowing through the combination coil is controlled by a dedicated rear thermal expansion valve.

The combination coil can be accessed for service by removing the rear heater-A/C unit upper housing. The combination coil cannot be repaired and, if faulty or damaged, it must be replaced.

UNDERBODY PLUMBING
The refrigerant lines and hoses are used to carry the refrigerant between the various air conditioning system components. A barrier hose design with a nylon tube, which is sandwiched between rubber layers, is used for the R-134a air conditioning system on this vehicle. This nylon tube helps to further contain the R-134a refrigerant, which has a smaller molecular structure than R-12 refrigerant. The ends of the refrigerant hoses are made from lightweight aluminum or steel, and commonly use braze-less fittings.

Any kinks or sharp bends in the refrigerant plumbing will reduce the capacity of the entire air conditioning system. Kinks and sharp bends reduce the flow of refrigerant in the system. A good rule for the flexible hose refrigerant lines is to keep the radius of all bends at least ten times the diameter of the hose. In addition, the flexible hose refrigerant lines should be routed so they are at least 80 millimeters (3 inches) from the exhaust manifold.

High pressures are produced in the refrigerant system when the air conditioning compressor is operating. Extreme care must be exercised to make sure that each of the refrigerant system connections is pressure-tight and leak free. It is a good practice to inspect all flexible hose refrigerant lines at least once a year to make sure they are in good condition and properly routed.

The refrigerant lines and hoses are coupled with other components of the HVAC system with peanut- block style fittings. A stat-O seal type flat steel gasket with a captured compressible O-ring, is used to mate plumbing lines with A/C components to ensure the integrity of the refrigerant system.

The refrigerant lines and hoses cannot be repaired and, if faulty or damaged, they must be replaced.

RECEIVER/DRIER
A single filter-drier unit is used for both the front-only A/C system, and for the combined front and rear A/C system.The filter-drier is mounted on the right side of the engine compartment in front of the heater-A/C housing. It is located in the liquid line between the condenser outlet and the evaporator inlet. Refrigerant enters the filter-drier as a high-pressure, high-temperature liquid.

The filter-drier performs a filtering action to prevent foreign material in the refrigerant from contaminating the expansion valve. A desiccant bag is mounted inside the filter-drier canister to absorb any moisture which may have entered and become trapped within the refrigerant system. In addition, during periods of high demand air conditioner operation, the filter-drier acts as a reservoir to store surplus liquid refrigerant.

The filter-drier cannot be repaired. If the filter- drier is faulty or damaged or if the refrigerant system has been contaminated, or if the system has been left open to the atmosphere for an indeterminable period, it must be replaced.

REFRIGERANT
The refrigerant used in this air conditioning system is a HydroFluoroCarbon (HFC), type R-134a. Unlike R-12, which is a ChloroFluoroCarbon (CFC), R-134a refrigerant does not contain ozone-depleting chlorine. R-134a refrigerant is a non-toxic, non-flammable, clear, and colorless liquefied gas.

Even though R-134a does not contain chlorine, it must be reclaimed and recycled just like CFC-type refrigerants. This is because R-134a is a greenhouse gas and can contribute to global warming.

R-134a refrigerant is not compatible with R-12 refrigerant in an air conditioning system. Even a small amount of R-12 added to an R-134a refrigerant system will cause compressor failure, refrigerant oil sludge or poor air conditioning system performance. In addition, the PolyAlkylene Glycol (PAG) synthetic refrigerant oils used in an R-134a refrigerant system are not compatible with the mineral-based refrigerant oils used in an R-12 refrigerant system.

R-134a refrigerant system service ports, service tool couplers and refrigerant dispensing bottles have all been designed with unique fittings to ensure that an R-134a system is not accidentally contaminated with the wrong refrigerant (R-12). There are also labels posted in the engine compartment of the vehicle and on the compressor identifying to service technicians that the air conditioning system is equipped with R-134a.

REFRIGERANT OIL
The refrigerant oil used in R-134a refrigerant systems is a synthetic-based, PolyAlkylene Glycol (PAG), wax-free lubricant. Mineral-based R-12 refrigerant oils are not compatible with PAG oils, and should never be introduced to an R-134a refrigerant system.

There are different PAG oils available, and each contains a different additive package. The TRS-105 compressor used in this vehicle is designed to use an SP-15 PAG refrigerant oil. Use only refrigerant oil of this same type to service the refrigerant system.

After performing any refrigerant recovery or recycling operation, always replenish the refrigerant system with the same amount of the recommended refrigerant oil as was removed. Too little refrigerant oil can cause compressor damage, and too much can reduce air conditioning system performance.

PAG refrigerant oil is much more hygroscopic than mineral oil, and will absorb any moisture it comes into contact with, even moisture in the air. The PAG oil container should always be kept tightly capped until it is ready to be used. After use, recap the oil container immediately to prevent moisture contamination.

WATER VALVE
Front
A vacuum-actuated water valve is installed in the heater hose between the engine and the front heater core in the engine compartment. Vacuum to the front heater core water valve is controlled by the rotary-type mode control vacuum switch in the heater-only or heater-A/C control.

The front water valve is a normally-open valve used to control engine coolant flow through the heater core. When vacuum is applied to the integral water valve vacuum actuator, the actuator closes the valve and coolant flow through the heater core is stopped. When the water valve is opened (no vacuum is applied), the coolant flows through the heater core and back to the engine.

The front water valve cannot be repaired and, if faulty or damaged, it must be replaced.

Rear
On models equipped with the optional rear heater- A/C unit, a cable-actuated rear water valve is located near the back of the rear unit housing. The rear water valve is installed in the rear unit heater hose between the engine and the rear combination coil. The rear water valve control cable is operated by the rear mode control motor.

The rear mode control motor is controlled by a momentary switch that is integral to the heater-A/C control. When the rotary-type temperature control knob is moved to a position that is at least 80 percent of its travel from the full cool position, the switch closes the signal circuit for the rear mode control motor to ground. This signal causes the rear mode control motor to move the rear heat-A/C mode door to the heat position and open the rear water valve. When the switch opens the signal circuit, the motor moves the rear heat-A/C mode door to the A/C position and closes the rear water valve.

The rear water valve cannot be repaired and, if faulty or damaged, it must be replaced.