Filter-drier. Heater and air conditioner



The filter-drier is mounted on the right front wheelhouse front extension in the engine compartment, 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 refrigerant.

The filter-drier cannot be repaired. If the filterdrier 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.

Heater and air conditioner


All vehicles are equipped with a common heater- A/C housing assembly (Fig. 4). The system combines air conditioning, heating, and ventilating capabilities in a single unit housing mounted under the instrument panel.

Fig. 4 Common Blend-Air Heater-Air Conditioner System - Typical Fig. 4 Common Blend-Air Heater-Air Conditioner System - Typical









Outside fresh air enters the vehicle through the cowl top opening at the base of the windshield, and passes through a plenum chamber to the heater-A/C system blower housing. Air flow velocity can then be adjusted with the blower motor speed selector switch on the heater-A/C control panel. The air intake openings must be kept free of snow, ice, leaves, and other obstructions for the heater-A/C system to receive a sufficient volume of outside air.

It is also important to keep the air intake openings clear of debris because leaf particles and other debris that is small enough to pass through the cowl plenum screen can accumulate within the heater-A/C housing. The closed, warm, damp and dark environment created within the heater-A/C housing is ideal for the growth of certain molds, mildews and other fungi. Any accumulation of decaying plant matter provides an additional food source for fungal spores, which enter the housing with the fresh air. Excess debris, as well as objectionable odors created by decaying plant matter and growing fungi can be discharged into the passenger compartment during heater-A/C system operation.

The heater and air conditioner are blend-air type systems. In a blend-air system, a blend-air door controls the amount of unconditioned air or cooled air from the evaporator that is allowed to flow through, or around, the heater core. A temperature control knob on the heater-A/C control panel determines the discharge air temperature by moving a cable, which operates the blend-air door. This allows an almost immediate manual control of the output air temperature of the system.

The mode control knob on the heater-A/C control panel is used to direct the conditioned air to the selected system outlets. The mode control switch uses engine vacuum to control the mode doors, which are operated by vacuum actuator motors.

The outside air intake can be shut off by selecting the recirculation mode (Max A/C) with the mode control knob. This will operate a vacuum actuated recirculating air door that closes off the outside fresh air intake and recirculates the air that is already inside the vehicle.

A large central duct delivers conditioned air from the front heater-A/C housing to the second and third seat floor panel foot wells. A damper door in this duct can be adjusted by the second seat passengers with a manual control located on a mini-console just behind the split bench seat center cushion, or located on the upper rear surface of the floor console on models with the optional bucket seats. The split bench seat control has two positions: On or Off. The bucket seat control has three positions: On, Off and a third position that directs air flow through a pair of adjustable barrel outlets mounted high on the rear surface of the floor console.

The air conditioner for all models is designed for the use of non-CFC, R-134a refrigerant. The air conditioning system has an evaporator to cool and dehumidify the incoming air prior to blending it with the  heated air. This air conditioning system uses a thermal expansion valve between the condenser and the evaporator coil to meter refrigerant flow to the evaporator coil. To maintain minimum evaporator temperature and prevent evaporator freezing, an electronic cycling clutch switch on the expansion valve cycles the compressor clutch.

    Dodge Durango (DN) 1998-2003 Service Manual


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