HVAC - Plumbing - Rear: Overview Dodge Durango II

Scheme 498

Scheme 499

DESCRIPTION

The rear heater core (1) is located in the rear HVAC housing (2), behind the right interior quarter panel trim. The rear heater core is a heat exchanger made of rows of tubes and fins.

If the rear heater core is found to be leaking or is damaged, it must be replaced.

OPERATION

Engine coolant is circulated through heater hoses/tubes 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 housing is directed through the heater core. The blower motor speed controls the volume of air flowing through the heater-A/C housing. The heater core cannot be repaired and, if faulty or damaged, it must be replaced. Refer to COOLING for more information on the engine cooling system, the engine coolant and the heater hoses.

Scheme 500

Scheme 501

1. Remove the rear HVAC housing (Refer to «HOUSING-HVAC»(ref-212854-S33367390112005122700000) ).
2. Remove the rear blend door actuator (Refer to «ACTUATOR-BLEND DOOR»(ref-212852-S15459776592005122700000) ).
3. Carefully remove the foam seal (1) from the rear heater core and evaporator extension line flange (3). If the seal is deformed or damaged, it must be replaced.
4. Remove the screws (2) that secure the two halves of the rear heater core and evaporator extension line flange together.
5. Remove the outer half of the rear heater core and evaporator extension line flange.
6. Remove the screw (1) that secures the rear heater core tube retaining bracket (2) to the rear HVAC housing (3).
7. Remove the rear heater core tube retaining bracket.
8. Carefully pull the rear heater core (4) out of the side of the rear HVAC housing.

Scheme 502

Scheme 503

1. Install the rear heater core (4) into the side of the rear HVAC housing (3). Make sure that the insulator is properly installed.
2. Install the rear heater core retaining bracket (2).
3. Install the screw (1) that secures the rear heater core retaining bracket to the rear HVAC housing. Tighten the screw to 2 N.m (17 in. lbs.).
4. Install the outer halve of the rear heater core and evaporator extension line flange (3).
5. Install the screws (2) that secure the two halves of the rear heater core and evaporator extension line flange together. Tighten the screws to 2 N.m (17 in. lbs.).
6. Install the foam seal (1) to the rear heater core and evaporator extension line flange.
7. Install the rear blend door actuator (Refer to «ACTUATOR-BLEND DOOR»(ref-212852-S15459776592005122700000) ).
8. Install the rear HVAC housing (Refer to «HOUSING-HVAC»(ref-212854-S33367390112005122700000) ).

Spring-lock type refrigerant line couplers (6) are used to connect the liquid line (1) and the suction line (3) to the underbody refrigerant lines for the rear heating-A/C system. Secondary retaining clips (2 and 7) are installed over the connected couplers for added protection.

The spring-lock refrigerant line couplers require special disconnect tools for disengaging the two coupler halves.

Scheme 504

The spring-lock type refrigerant line coupler is held together by a garter spring (6) inside a circular cage (7) on the male half of the fitting (1). When the two coupler halves are connected, the flared end of the female fitting (2) slips behind the garter spring inside the cage on the male fitting. The garter spring and cage prevent the flared end of the female fitting from pulling out of the cage.

Two O-rings (8) are used to seal the coupler connection. These O-rings are compatible with R-134a refrigerant and must be replaced with O-rings made of the same material.

A secondary retaining clip (3) is installed over the connected coupler (5) for added protection.

Scheme 505

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

Scheme 506

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

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

Scheme 507

1. Remove the rear HVAC housing (1) and place it on a workbench (Refer to «HOUSING-HVAC»(ref-212854-S33367390112005122700000) ).
2. Disconnect the rear HVAC wire harness (2) from the rear blower motor (3) and the rear blower motor resistor block (4).
3. Remove the screws (5) that secure the rear air inlet housing (6) to the rear HVAC housing.
4. Remove the rear air inlet housing from the rear HVAC housing.
5. Remove the insulator (1) from around the rear A/C evaporator tubes (2) to gain access the two rear A/C expansion valve bolts (3).
6. Remove the two bolts that secure the rear A/C evaporator tubes to the rear A/C expansion valve (4) and the rear evaporator extension tube tapping block (5).
7. Carefully lift the rear A/C evaporator (6) out of the top of the rear HVAC housing (7).
8. Remove the rear A/C expansion valve from the rear evaporator extension tube tapping block.
9. Remove the O-ring seals from the rear A/C evaporator tubes and extension tube fittings and discard.
10. Install plugs in, or tape over the opened tube fittings and all rear expansion valve ports.

The liquid line (1) is the refrigerant line that carries refrigerant from the A/C condenser to the rear A/C evaporator. The liquid line serviced in two sections and includes a tapping plate (4) that retains the suction line (3) (Refer to LINE-A/C LIQUID ). Models equipped with the rear heating-A/C system include an extension tube (8) that connects the liquid line to the underbody line by use of a spring-lock type refrigerant line coupler (6) and a secondary retaining clip (7).

The liquid 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 liquid line is removed and installed.

Scheme 508

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

The suction line (3) is the refrigerant line that carries refrigerant from the rear A/C evaporator to the A/C compressor. The suction line is retained into the liquid line tapping block (4) by a plastic retainer (Refer to LINE-A/C SUCTION ). Models equipped with the rear heating-A/C system include an extension tube (5) that connects the suction line to the underbody line by use of a spring-lock type refrigerant line coupler (6) and a secondary retaining clip (2).

The suction 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 suction line is removed and installed.

Scheme 509

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

An auxiliary electric coolant pump is used on all models to aid in circulating the engine coolant through the front and rear heater core (depending on application). The electric coolant pump is mounted to the right front frame rail by a rubber isolator (1) and consists of a molded plastic housing (2) with two heater hose connections (3), a 12 volt direct current (DC) motor and impeller assembly (4) with an integral wire connector receptacle (5).

Scheme 510

The A/C-heater control operates the electric coolant pump when all of the following conditions have been met.

1. Vehicle speed below 48 km/h (30 mph)
2. Coolant temperature between 10°C (50°F) and 110°C (230°F)
3. Front blower motor turned On
4. Rear temperature heat setting above the halfway setting (60% heat)
5. No fault conditions detected

The A/C-heater control turns the electric coolant pump Off when any of the following conditions occur.

1. Vehicle speed above 48 km/h (30 mph)
2. Coolant temperature above 110°C (230°F)
3. Front blower motor turned Off

The electric coolant pump cannot be adjusted or repaired and, if faulty or damaged, it must be replaced.

The electric coolant pump is diagnosed using a scan tool. Refer to HVAC - ELECTRICAL DIAGNOSTICS for more information.

The rear A/C expansion valve is of a thermostatic expansion valve (TXV) design and controls the amount of refrigerant entering the rear A/C evaporator. The rear A/C expansion valve consists of an aluminum H-valve type body (1) with an integral thermal sensor (2) and is located on the rear HVAC housing between the rear evaporator extension tubes and the rear evaporator.

Scheme 511

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

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

See also:
• LINER-FRONT FENDER
• PANEL-QUARTER TRIM