HVAC - Plumbing - Front: Overview Dodge Durango II

DESCRIPTION

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

Any kinks or sharp bends in the refrigerant lines and hoses will reduce the capacity of the entire A/C system and can reduce the flow of refrigerant in the system. The radius of all bends in the flexible hose refrigerant lines should be at least ten times the diameter of the hose and the refrigerant lines should be routed so they are at least 80 millimeters (3 inches) away from the exhaust manifold(s) and exhaust pipe(s).

OPERATION

High pressures are produced in the refrigerant system when the A/C 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 to other A/C system components with block-type fittings. An O-ring seal and a flat steel gasket are used to mate the refrigerant line fittings with A/C system 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.

The A/C condenser (2) is located in the front of the engine compartment inside of the condenser fan shroud (3). The A/C condenser is a heat exchanger that allows the high-pressure refrigerant gas being discharged by the A/C compressor to give up its heat to the air passing over the condenser fins, which causes the refrigerant to change to a liquid state.

The A/C condenser is retained within the condenser fan shroud by two bolts (1).

Scheme 433

When air passes through the fins of the A/C condenser, the high-pressure refrigerant gas within the A/C condenser gives up its heat. The refrigerant then condenses as it leaves the A/C condenser and becomes a high-pressure liquid. The volume of air flowing over the condenser fins is critical to the proper cooling performance of the A/C system. Therefore, it is important that there are no objects placed in front of the radiator grille openings at 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 A/C condenser service.

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

The heater core (1) for the front heating-A/C system is located in the front HVAC housing, behind the instrument panel. It is a heat exchanger made of rows of tubes and fins. The heater core is secured to the HVAC housing by a plastic retaining bracket (2) and the heater core tubes (3) are attached to the top of the heater core by a bolt (5).

The heater core for the front heating-A/C system can be serviced in the vehicle without removing the HVAC assembly.

Scheme 434

Engine coolant is circulated through the heater hoses to the heater core at all times. As the coolant flows through the heater core, heat is removed from the engine and 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 regulating the amount of air flowing through the heater core within the HVAC housing. The blower motor speed controls the volume of air flowing through the HVAC housing.

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

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1. Drain the engine cooling system (Refer to «DRAINING COOLING SYSTEM - ALL ENGINES»(ref-212747-S18408552002005122700000) ).
2. Raise and support the vehicle.
3. Remove the right front wheelhouse splash shield (Refer to «LINER-FRONT FENDER»(ref-212840-S40194930252005122700000) ).
4. Remove the heater hoses (1) from the heater core tubes (2) in the engine compartment.
5. Lower the vehicle and remove the instrument panel (Refer to «ASSEMBLY-INSTRUMENT PANEL»(ref-212841-S41548306542005122700000) ).
6. Remove the bolt (1) that secures the HVAC housing bracket (2) to the dash panel (5).
7. Remove the two screws (4) that secure the HVAC housing bracket to the top of the HVAC housing (3).
8. Remove the HVAC housing bracket from the vehicle.
9. Remove the screw (1) that secures the heater core tube retaining bracket (2) to the top of the HVAC housing (3).
10. Remove the heater core tube retaining bracket from the HVAC housing.
11. Remove the screw (4) that secures the heater core tubes (6) to the heater core (5).
12. Remove the heater core tubes from the heater core and the dash panel. Remove the O-ring seals from the heater core tube fittings and discard.
13. Remove the two screws (1) that secure the heater core retaining bracket (2) to the top of the HVAC housing (3).
14. Remove the heater core retaining bracket from the top of the HVAC housing.
15. Carefully lift the heater core (4) out of the HVAC housing.

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1. Carefully install the heater core (4) and the heater core retaining bracket (2) to the top of the HVAC housing (3). Make sure that the heater core insulator is properly positioned.
2. Install the two screws (1) that secure the heater core and retaining bracket to the HVAC housing. Tighten the screws to 2.2 N.m (20 in. lbs.).
3. Lubricate new rubber O-ring seals with clean engine coolant and install them onto the heater core tube fittings. Use only the specified O-ring as it is made of a special material for the engine cooling system.
4. Install the heater core tubes (6) through the dash panel and to the heater core (5).
5. Install the screw (4) that secures the heater core, tubes to the heater core. Tighten the screw securely.
6. Install the heater core tube retaining bracket (2) to the top of the HVAC housing (3).
7. Install the screw (1) that secures the heater core tube retaining bracket to the HVAC housing. Tighten the screw to 2.2 N.m (20 in. lbs.).
8. Install the HVAC housing bracket (2) to the top of HVAC housing (3) and to the dash panel (5).
9. Install the two screws (4) that secure the HVAC housing bracket to the HVAC housing. Tighten the screws to 2.2 N.m (20 in. lbs.).
10. Install the bolt (1) that secures the HVAC housing bracket to the dash panel. Tighten the bolt to 3 N.m (26 in. lbs.).
11. Install the instrument panel (Refer to «ASSEMBLY-INSTRUMENT PANEL»(ref-212841-S41548306542005122700000) ).
12. Raise the vehicle and install the heater hoses (1) to the heater core tubes (2) in the engine compartment
13. Install the right front wheelhouse splash shield (Refer to «LINER-FRONT FENDER»(ref-212840-S40194930252005122700000) ).
14. Lower the vehicle.
15. Refill the engine cooling system (Refer to «REFILLING COOLING SYSTEM»(ref-212747-S15342466592005122700000) ).

Two refrigerant system service ports are used to recover/recycle/evacuate/charge and test the A/C refrigerant system. Unique sizes are used on the service ports for the R-134a refrigerant system to ensure the system is not accidentally contaminated with R-12 refrigerant or service equipment used for R-12 refrigerant.

The high side service port (5) is located on the liquid line (3) above the receiver/drier (2). The low side service port (6) is located on the suction line (9) at the top of the engine. Both the high side and low side A/C service port valve cores are serviceable.

Each of the service ports has a threaded plastic protective cap installed over it from the factory. After servicing the refrigerant system, always reinstall both of the service port caps.

Scheme 443

The A/C evaporator (1) for the front heating-A/C system is located within the front HVAC housing (2), behind the instrument panel. The A/C evaporator and insulator (3) are positioned in the HVAC housing so that all air entering the housing must pass over the evaporator fins before it is distributed through the heating-A/C system ducts and outlets. However, air passing over the evaporator fins will only be conditioned when the A/C compressor is engaged and circulating refrigerant through the A/C evaporator.

Scheme 444

Refrigerant enters the A/C evaporator from the A/C expansion valve as a low-temperature, low-pressure mixture of liquid and gas. As air flows over the fins of the A/C 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 A/C evaporator.

The A/C evaporator cannot be repaired and, if faulty or damaged, it must be replaced.

Scheme 445

1. Remove the HVAC housing (Refer to «HOUSING-HVAC»(ref-212853-S30259552272005122700000) ).
2. Disassemble the HVAC housing (Refer to «HOUSING-HVAC»(ref-212853-S30259552272005122700000) ).
3. Remove the probe of the evaporator temperature sensor from the fins of the A/C evaporator (Refer to «SENSOR-EVAPORATOR TEMPERATURE»(ref-212851-S25345641672005122700000) ).
4. Carefully lift the A/C evaporator (1) out of the lower half of the HVAC housing (2).
5. If required, remove the evaporator insulator (3) from around the A/C evaporator.

The A/C discharge line (1) is the refrigerant line that carries refrigerant from the A/C compressor to the A/C condenser (2) and is secured to the condenser fan shroud (4) by a plastic retainer (3). The A/C discharge line has an integral fitting for the A/C pressure transducer (5) (Refer to TRANSDUCER-A/C PRESSURE ).

The A/C discharge line has no serviceable parts except for the rubber O-ring seals. The O-ring seals used on the connections are made from a special type of rubber not affected by R-134a refrigerant. The O-ring seals must be replaced whenever the A/C discharge line is removed and installed.

If the A/C discharge line is found to be leaking or is damaged, it must be replaced.

Scheme 446

The liquid line is the refrigerant line that carries refrigerant from the A/C condenser to the A/C evaporator. The liquid line is serviced in two sections. The front section of the liquid line (1) connects between the A/C condenser and the receiver/drier (2). The rear section of the liquid line (3) connects between the receiver/drier and the A/C expansion valve (7) and includes the high side service port (5) and a tapping plate (8) that secures the suction line (9) to the A/C expansion valve. On models equipped with the rear heating-A/C system, the rear section of the liquid line also includes an extension tube that connects the liquid line to the underbody lines (Refer to LINE-A/C LIQUID ).

Scheme 447

The liquid line has no serviceable parts except for the rubber O-ring seals, high-side service port valve, cap and retainer clip (4). The O-ring seals used on the connections are made from a special type of rubber not affected by R-134a refrigerant. The O-ring seals must be replaced whenever the liquid line is removed and installed.

If the liquid line is found to be leaking or is damaged, it must be replaced.

The suction line (9) is the refrigerant line that carries refrigerant from the A/C evaporator to the A/C compressor. The suction line includes the low side service port (6) and is secured to the A/C expansion valve (7) by the liquid line tapping plate (8). On models equipped with the rear heating-A/C system, the suction line also includes an extension tube that connects the suction line to the underbody lines (Refer to LINE-A/C SUCTION ).

Scheme 448

The suction line has no serviceable parts except for the rubber O-ring seals, low-side service port valve and cap. The O-ring seals used on the connections are made from a special type of rubber not affected by R-134a refrigerant. The O-ring seals must be replaced whenever the suction line is removed and installed.

If the suction line is found to be leaking or is damaged, it must be replaced.

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 Denso 10S20 A/C compressor used in this vehicle is designed to use ND-8 PAG refrigerant oil. Use only this type of refrigerant oil in 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 A/C compressor damage, and too much can reduce A/C system performance.

PAG refrigerant oil is 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.

The receiver/drier (1) is mounted in a bracket (2) secured to the right front frame rail (4) in the engine compartment. The receiver/drier is connected between the front section of the liquid line (3) and the rear section of the liquid line (5) between the condenser outlet and the evaporator inlet.

Scheme 449

The receiver/drier performs a filtering action to prevent foreign material in the refrigerant from contaminating the A/C expansion valve. Refrigerant enters the receiver/drier as a high-pressure, low temperature liquid. Desiccant inside the receiver/drier absorbs any moisture which may have entered and become trapped within the refrigerant system. In addition, during periods of high demand operation of the A/C system, the receiver/drier acts as a reservoir to store surplus refrigerant.

The receiver/drier cannot be repaired. If the receiver/drier is faulty or damaged, or if the refrigerant system has been contaminated or left open to the atmosphere for an indeterminable period or if the A/C compressor has failed, it must be replaced.

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 A/C system. Even a small amount of R-12 refrigerant added to an R-134a refrigerant system will cause A/C compressor failure, refrigerant oil sludge or poor A/C 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 refrigerant 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 A/C compressor to identify that the A/C system is equipped with R-134a refrigerant.

The A/C expansion valve controls the amount of refrigerant entering the A/C evaporator and is of a thermostatic expansion valve (TXV) design. The A/C expansion valve consists of an aluminum H-valve type body (1) with an integral thermal sensor (2) and is located at the dash panel between the A/C refrigerant lines and the A/C evaporator.

Scheme 450

The A/C expansion valve controls the high-pressure, low temperature liquid refrigerant from the liquid line and converts it into a low-pressure, low-temperature mixture of liquid and gas before it enters the A/C evaporator. A mechanical sensor in the A/C expansion valve monitors the temperature and pressure of the refrigerant leaving the A/C evaporator through the suction line, and adjusts the orifice size at the liquid line port to let the proper amount of refrigerant into the A/C evaporator to meet the vehicle A/C cooling requirements. Controlling the refrigerant flow through the A/C evaporator ensures that none of the refrigerant leaving the A/C evaporator is still in a liquid state, which could damage the A/C compressor.

The A/C expansion valve is factory calibrated and cannot be adjusted or repaired and, if faulty or damaged, it must be replaced.