Part 2B

REAR AIR OUTLETS
Based upon the system mode selected, conditioned air can exit the rear heater-A/C unit housing through one or a combination of the two main housing outlets: air conditioner, or heater. Once the conditioned air exits the unit housing, it is directed through molded plastic ducts to the various outlets in the vehicle interior. These outlets and their locations are as follows:
- Floor Outlets - Three floor outlets with fixed vanes are located in the right quarter trim panel, near the floor. These outlets distribute air from the rear heater distribution duct to the intermediate and rear seat occupants. The floor outlets are integral to the right quarter trim panel and, if faulty or damaged, the quarter trim panel must be replaced.
- Overhead Outlets - Four (two right side and two left side) fully adjustable outlets along the roof rails distribute air from the rear A/C distribution duct and the headliner ducts to the intermediate and rear seat occupants. The headliner ducts are integral to the headliner panel. Each overhead outlet is housed in a headliner bezel. The two forward headliner bezels also feature a courtesy lamp, a fold-away coat hook, and a fold-away assist handle. The overhead outlets can be removed from the headliner bezels individually for service replacement.

Fig.3 Blower Motor:

REAR BLOWER MOTOR
The blower motor is a 12-volt, Direct Current (DC) motor with a squirrel cage-type blower wheel that is secured to the blower motor shaft. The blower motor and wheel are located in a housing near the top of the rear heater-A/C unit in the passenger compartment behind the right rear wheel house. The rear heater-A/C unit housing must be removed from the vehicle to access the blower motor and blower wheel for service. The blower motor and blower motor wheel are a factory balanced unit and cannot be adjusted or repaired. If faulty or damaged, the blower motor and blower wheel must be replaced as a unit.

The rear blower motor will operate whenever the ignition switch is in the ON position, the heater-A/C control power is turned ON, and the rear heater-A/C system control switch on the front heater-A/C control is not in the OFF position. The blower motor can only be turned OFF by turning off the rear system at the front heater-A/C control. The blower motor receives battery current whenever the rear blower motor relay is energized. The rear blower motor relay output circuit is protected by a fuse in the Intelligent Power Module (IPM) located in the engine compartment near the battery. In the MTC system, the blower motor speed is controlled by regulating the path to ground through the blower control switch and the blower motor resistor. In the ATC system, the blower motor speed is controlled by an electronic blower power module, which uses a pulse width modulated input from the ATC module and feedback from the blower motor to regulate the blower motor ground path it provides. The blower motor and wheel are used to control the velocity of air moving through the rear heater-A/C unit housing. The blower motor controls the velocity of the air flowing through the rear heater-A/C housing by spinning the blower wheel within the housing at the selected speed or, in the ATC system, at the selected or programmed speed.

COMPRESSOR
The compressor used on this vehicle can be one of two models, depending upon the air conditioning system in the vehicle. All vehicles use the Nippondenso 10S20 compressor. This compressor use an aluminum swash plate, teflon coated pistons and aluminum sleeveless cylinder walls. This compressor includes an integral high pressure relief valve. The compressor is secured low in the right front corner of the engine compartment to a mounting bracket on the cylinder block (2.4L engine), or directly to the cylinder block (3.3L and 3.8L engines) is integral to the compressor. This compressor cannot be repaired. If faulty or damaged, the entire compressor must be replaced. The compressor clutch, pulley, and clutch coil are available for service replacement.

The compressor is driven by the engine through an electric clutch, drive pulley and belt arrangement. The compressor is lubricated by refrigerant oil that is circulated throughout the refrigerant system with the refrigerant. The compressor draws in low-pressure refrigerant vapor from the evaporator through its suction port. It then compresses the refrigerant into a high-pressure, high-temperature refrigerant vapor. The compressor pumps high-pressure refrigerant vapor to the condenser through the compressor discharge port. The mechanical high pressure relief valve is designed to vent refrigerant from the system to protect against damage to the compressor or other system components, caused by condenser air flow restrictions or an overcharge of refrigerant. The valve only vents enough refrigerant to reduce the system pressure, then re-seats itself. The valve opens at a discharge pressure of 3445 - 4135 kPA (500 - 600 psi) or above, and closes when a minimum discharge pressure of 2756 kPa (400 psi) is reached.

CONDENSER
The condenser is integral to a cooling module which includes the radiator, the electric cooling fan, the fan shroud, air seals and an automatic transmission oil cooler. The cooling module is located in the air flow in the front of the engine compartment behind the radiator grille. The condenser cannot be repaired or adjusted and, if faulty or damaged, it must be replaced. The condenser may be removed from the cooling module for service without removing the cooling module from the vehicle.

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 air flow. Also, any factory-installed air seals or shrouds must be properly reinstalled following radiator or condenser service.

FRONT EVAPORATOR
The evaporator is located in the heater-A/C unit housing, behind the instrument panel. The evaporator 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 fins will only be conditioned when the compressor is engaged and circulating refrigerant through the evaporator tubes. The heater-A/C unit housing must be removed from the vehicle to access the evaporator for service. The evaporator cannot be adjusted or repaired and, if faulty or damaged, it must be replaced.

Refrigerant enters the evaporator from the expansion valve as a low-temperature, low-pressure liquid/ vapor mixture. 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 when it leaves the evaporator.

FRONT EXPANSION VALVE
The front "H" valve-type Thermal Expansion Valve (TXV) is located at the dash panel between the liquid and suction lines, and the evaporator coil. The assembly consists of an H-valve body and a thermal sensor. High-pressure, low 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. The expansion valve is a factory calibrated unit and cannot be adjusted or repaired. If faulty or damaged, the expansion valve must be replaced.

A mechanical sensor in the expansion valve control head monitors the temperature and pressure 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 thermo sensor measures refrigerant suction gas temperature which is monitored by the a/c control assembly.

FRONT HEATER CORE
The heater core is located in the distribution housing of the heater-A/C unit, under the instrument panel. It is a heat exchanger made of rows of tubes and fins. One end of the core is fitted with a molded plastic tank that includes integral heater core inlet and outlet ports. The removable heater core tubes are held in place these ports by a sealing plate secured with a screw to the heater core tank. This removable heater core tube arrangement allows the heater core to be serviced without removing the heater-A/C unit housing from the vehicle. The heater core cannot be repaired and, if faulty or damaged, it must be replaced.

Engine coolant is circulated through heater hoses to the heater core at all times. As the coolant flows through the heater core, heat removed from the engine is transferred to the heater core fins and tubes. Air directed through the heater core picks up the heat from the heater core fins. 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 unit housing is directed through the heater core.

RECEIVER/DRIER
The filter-drier is mounted in a bracket secured to the right front strut tower in the engine compartment. The filter-drier is connected between the front and rear sections of the liquid line between the condenser outlet and the evaporator inlet. The filter- drier cannot be repaired. If the filter-drier is faulty or damaged, or if the refrigerant system has been contaminated or left open to the atmosphere for an indeterminable period, it must be replaced.

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 refrigerant. Refrigerant enters the filter-drier as a high-pressure, low temperature liquid.

REFRIGERANT
The refrigerant used in this air conditioning system is a HydroFluoroCarbon (HFC), type R-134a. Unlike R-12, which is a ChloroFluoroCarboncle (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 10S20H compressor used in this vehicle are designed to use an ND-8 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.

REAR EVAPORATOR
The rear evaporator is located in the rear heater A/C unit housing, behind the right rear wheel house. The evaporator is positioned in the rear 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. Flow- ever, air passing over the evaporator fins will only be conditioned when the compressor is engaged and circulating refrigerant through the evaporator tubes. The rear heater-A/C unit housing must be removed from the vehicle to access the evaporator for service. The evaporator cannot be adjusted or repaired and, if faulty or damaged, it must be replaced.

Refrigerant enters the rear evaporator from the rear expansion valve as a low-temperature, low-pressure liquid. 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 when it leaves the evaporator.

REAR EXPANSION VALVE
The rear "H" valve-type thermal expansion valve (TXV) is located at the rear of the rear heater-A/C unit housing between the evaporator line extension and the evaporator coil. High-pressure, low 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. The expansion valve is a factory calibrated unit and cannot be adjusted or repaired. If faulty or damaged, the expansion valve must be replaced.

A mechanical sensor in the expansion valve control head monitors the temperature and pressure 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.

REAR HEATER CORE
The rear heater core is located near the front of the rear heater-A/C unit housing, behind the right rear wheel house. It is a heat exchanger made of rows of tubes and fins. One end of the core is fitted with a molded plastic tank that includes integral heater core inlet and outlet nipples. The heater core can be serviced without removing the rear heater-A/C unit housing from the vehicle. The heater core cannot be repaired and, if faulty or damaged, it must be replaced.

Engine coolant is circulated through heater hoses to the heater core at all times. As the coolant flows through the heater core, heat removed from the engine is transferred to the heater core fins and tubes. Air directed through the heater core picks up the heat from the heater core fins. The blend air door allows control of the heater output air temperature by controlling how much of the air flowing through the rear heater-A/C unit housing is directed through the heater core.

UNDERBODY LINES
The rear heater-A/C unit plumbing is used only on models with the optional rear heater-A/C unit. The formed metal rear heater-A/C unit suction line, liquid line, and heater lines are available for separate service replacement. The molded and straight heater hoses used on the rear heater-A/C unit can be serviced in the vehicle.

Fig.8 Rear Heater And A/C Lines:

Fig. 9 Front Lines Connected To Rear Lines:

Fig.11 Rear Heater Hose Quick Connects:

Fig.10 Rear Heater Hose Connection:

Fig.12 Rear A/C Block Connection:

The rear heater and A/C lines are all serviced as individual pieces. When disconnecting any line or block ensure that the area around it is clean of any contaminations that can get in to the system,,, and.

Any kinks or sharp bends in the rear heater-A/C unit plumbing will reduce the capacity of the entire heating and air conditioning system. Kinks and sharp bends reduce the system flow. High pressures are produced in the refrigerant system when the air conditioning compressor is operating. High temperature coolant is present in the heater plumbing when the engine is operating. Extreme care must be exercised to make sure that each of the plumbing connections is pressure-tight and leak free.