HVAC Systems - Service Information: Overview Dodge Durango II рестайлинг

DESCRIPTION - HEATER AND AIR CONDITIONER

A manual temperature control (MTC) front single zone type heating-A/C system, MTC front and rear heating-A/C system and a front dual zone ATC and rear heating-A/C system is available on this vehicle.

To maintain the performance level of the heating, ventilation and air conditioning (HVAC) system, the engine cooling system must be properly maintained. The use of a bug screen is not recommended. Any obstructions in front of the radiator or A/C condenser will reduce the performance of the A/C and engine cooling systems.

The engine cooling system includes the radiator, thermostat, radiator hoses and the engine coolant pump. Refer to COOLING article for more information before opening or attempting any service to the engine cooling system.

Scheme 7

All vehicles are equipped with a common front heater, ventilation and air conditioning (HVAC) housing (1). The front heating-A/C system combines A/C, heating, and ventilating capabilities in a single HVAC housing mounted within the passenger compartment under the instrument panel. The front HVAC housing includes

1. Recirculation-air door and actuator (2)
2. Blower motor (3)
3. Blower motor resistor (MTC) or blower motor power module (ATC) (4)
4. Evaporator temperature sensor (5)
5. Blend-air door and actuator (6) (single zone or dual zone driver side)
6. Blend-air door and actuator (7) (dual zone passenger side)
7. Mode-air doors and actuators (8)
8. Heater core (9)
9. A/C evaporator (10)

Based upon the mode selected, conditioned air can exit the front HVAC housing through one or a combination of the three main housing outlets: defrost, panel or floor. The defrost outlet is located on the top of the HVAC housing, the panel outlet is located on the top of the HVAC housing and the floor outlet is located on the bottom of the HVAC housing. Once the conditioned air exits the HVAC housing, it is further directed through molded plastic ducts to the outlets within the vehicle interior. These outlets and their locations are as follows

1. Defroster Outlet - A single large defroster outlet is located in the center of the instrument panel top cover, near the base of the windshield.
2. Side Window Demister Outlets - There are two side window demister outlets, one is located at each outboard end of the instrument panel top cover, near the belt line at the A-pillars.
3. Panel Outlets - There are six panel outlets in the instrument panel, one located near each outboard end of the instrument panel facing the rear of the vehicle and two located at each side of the instrument panel center bezel.
4. Floor Outlets - There are four floor outlets, one located above each side of the floor panel center tunnel near the dash panel and one behind each front seat.

Scheme 8

The front manual temperature control (MTC) and rear heating-A/C system, and the single zone and dual zone front automatic temperature control (ATC) and rear heating-A/C systems are equipped with a common rear heater and A/C housing (1) that combines A/C and heating capabilities into a single unit mounted within the passenger compartment behind the right quarter interior trim panel. The rear HVAC housing includes

1. Blower motor (2)
2. Blower motor resistor (3)
3. A/C evaporator (4)
4. A/C expansion valve (5)
5. Heater core (6)
6. Blend door and actuator (7)
7. Mode door and actuator (8)

Based upon the rear temperature selected, conditioned air can exit the rear HVAC housing through one or a combination of the two rear HVAC housing outlets: ceiling or floor. The ceiling outlet is located at the top-front of the HVAC housing and the floor outlet is located at the front of the HVAC housing. Once the conditioned air exits the rear HVAC housing, it is further directed through molded plastic ducts to the outlets at the rear of the passenger compartment. These outlets and their locations are as follows

1. Ceiling Outlets - There are four ceiling outlets in the headliner. One located at each outboard side of the intermediate seat position and one located in front of each rear seat position.
2. Floor Outlet - There is one floor outlet in the right quarter interior trim panel located behind the right rear door area.

OPERATION - HEATER AND AIR CONDITIONER

The standard front and available rear heating-A/C systems used in this vehicle are blend-air type systems. In a blend-air system, a blend-air door controls the amount of conditioned air that is allowed to flow through, or around, the heater core. In the available front dual zone system, separate blend-air doors are used to provide completely independent side-to-side temperature control of the discharge air. The temperature control(s) determines the discharge air temperature(s) by operating the blend door actuator(s), which move the blend-air door(s). This design allows almost immediate control of output air temperature(s).

Scheme 9

The standard front heating-A/C system pulls outside (ambient) air through the fresh air intake (4) located at the cowl panel at the base of the windshield and into the air inlet housing above the heating, ventilation and air conditioning (HVAC) housing and then passes through the A/C evaporator (7). Air flow is then directed either through or around the heater core (2). This is done by adjusting the position of the blend-air door(s) (3) with the temperature control(s) located on the A/C-heater control in the instrument panel. Air flow is then directed out the floor outlet (8), instrument panel outlet (10) or the defroster outlet (1) in various combinations by adjusting the position of the mode-air doors (9 and 11) using the mode control located on the A/C-heater control. The temperature and mode control uses electrical actuators to operate the air doors.

The velocity of the air flow out of the outlets can be adjusted with the blower speed control located on the A/C-heater control.

The fresh air intake can be shut off by pressing the Recirculation button on the A/C-heater control. This will operate the electrically actuated recirculation-air door (5), which closes off the fresh air intake. With the fresh air intake closed, the conditioned air within the vehicle is pulled back into the HVAC housing through the recirculation air intake (6) located within the passenger compartment.

The A/C compressor can be engaged by pressing the A/C (snowflake) button on the A/C-heater control. It will automatically engage when the mode control is set in any Mix to Defrost position. This will remove heat and humidity from the air before it is directed through or around the heater core. The mode control on the A/C-heater control is used to direct the conditioned air to the selected system outlets.

The defroster outlet receives airflow from the HVAC housing through the molded plastic defroster duct, which connects to the HVAC housing defroster outlet. The airflow from the defroster outlet is directed by fixed vanes in the defroster outlet grille and cannot be adjusted. The defroster outlet grille is integral to the instrument panel top cover.

The side window demister outlets receive airflow from the HVAC housing through the molded plastic demister ducts. The demisters direct air from the HVAC housing through the outlets located on the top corners of the instrument panel. The airflow from the side window demister outlets is directed by fixed vanes in the demister outlet grilles and cannot be adjusted. The side window demister outlet grilles are serviceable from the instrument panel. The demisters operate when the mode control is positioned in the bi-level, floor, floor-defrost and defrost settings.

The instrument panel outlets receive airflow from the HVAC housing through a molded plastic main panel duct, center panel duct and two end panel ducts. The two end panel ducts direct airflow to the left and right instrument panel outlets, while the center panel duct directs airflow to the four center panel outlets. Each of these outlets can be individually adjusted to direct the flow of air.

The floor outlets receive airflow from the HVAC housing through the floor distribution ducts. The front floor outlets are integral to the molded plastic floor distribution duct, which is secured to the bottom of the HVAC housing. Two plastic rear floor distribution ducts attach to the floor distribution duct and provide conditioned air to the intermediate seating positions. The floor outlets cannot be adjusted.

Note. It is important to keep the air intake opening clear of debris. Leaf particles and other debris that is small enough to pass through the cowl opening screen can accumulate within the HVAC housing. The closed, warm, damp and dark environment created within the 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 intake-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 operation if the air intake opening is not kept clear of debris.

The front A/C system is designed for use of non-CFC, R-134a refrigerant and uses an A/C expansion valve (TXV) to meter the flow of refrigerant to the A/C evaporator. To maintain minimum evaporator temperature and prevent evaporator freezing, an evaporator temperature sensor input is supplied to the A/C-heater control. In turn, the powertrain control module (PCM) cycles the A/C compressor clutch off and on as necessary to optimize A/C system performance and to protect the A/C system from evaporator freezing.