Heater and Air Conditioning

A manually controlled single zone type heating-air conditioning system or a manually controlled dual zone type heating-air conditioning system is available on this model.

HVAC Housing - Dual Zone Shown, Single Zone Typical:

All vehicles are equipped with a common heater, ventilation and air conditioning (HVAC) housing. The system combines air conditioning, heating, and ventilating capabilities in a single unit housing mounted within the passenger compartment under the instrument panel. The HVAC housing includes:
- Blower motor
- Blower motor resistor block
- Heater core
- Evaporator coil
- Blend door and actuator
- Defrost door and actuator
- Mode door and actuator
- Recirculation door and actuator

Based upon the system and mode selected, conditioned air can exit the 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 housing, the panel outlet is located on the face of the housing and the floor outlet is located on the bottom of the housing. Once the conditioned air exits the unit housing, it is further directed through molded plastic ducts to the various outlets in the vehicle interior. These outlets and their locations are as follows:
- Defroster Outlet - A single large defroster outlet is located in the center of the instrument panel top cover, near the base of the windshield.
- 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.
- Panel Outlets - There are four 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 near the top of the instrument panel center bezel.
- Front Floor Outlets - There are two front floor outlets, one located above each side of the floor panel center tunnel near the dash panel.

The heating and air conditioning systems pulls outside (ambient) air through the cowl opening at the base of the windshield, then into the plenum chamber above the heating, ventilation and air conditioning (HVAC) housing. On models equipped with air conditioning, the air passes through the evaporator coil. Air flow can be directed either through or around the heater core. This is done by adjusting the blend door with the temperature control knob on the A/C-heater control located the instrument panel. The air flow can then be directed from the panel, floor and defrost outlets in various combinations using the mode control knob located on the A/C-heater control. Air flow velocity can be adjusted with the blower speed selector located on the A/C-heater control.

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 heater and air conditioning systems are blend-air type systems. In a blend-air system, a blend door controls the amount of unconditioned air (or cooled air from the evaporator on models with air conditioning) that is allowed to flow through, or around, the heater core. A temperature control knob determines the discharge air temperature by actuating an electric motor, which operates the blend door. This allows an almost immediate control of the output air temperature of the system.

On all models, the outside air intake can be shut off by selecting the Recirculation Mode with the mode control knob. This will operate a electric actuated recirculation air door that closes off the outside fresh air intake and recirculates the air that is already inside the vehicle.

The air conditioning compressor can be engaged in any mode by pressing the snowflake, A/C on/off button. It can also be engaged by placing the mode control in the mix to defrost positions. This will remove heat and humidity from the air before it is directed through or around the heater core. The mode control knob on the A/C-heater control is used to also direct the conditioned air to the selected system outlets. The mode control switch uses an electric motor to control the mode doors.

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 outlets is directed by fixed vanes in the defroster outlet grilles and cannot be adjusted. The defroster outlet grilles are integral to the instrument panel top cover.

The side window demister outlets receive airflow from the HVAC housing through the molded plastic defroster duct and two molded plastic demister ducts. 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 integral to the instrument panel. The demisters direct air from the HVAC housing through the outlets located on the top corners of the instrument panel. The demisters operate when the mode control knob is positioned in the floor-defrost and defrost-only settings. Some air may be noticeable from the demister outlets when the mode control is in the bi-level to floor positions.

The 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 two 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 duct. The front floor outlets are integral to the molded plastic floor distribution duct, which is secured to the bottom of the housing. The floor outlets cannot be adjusted.

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 fixed orifice tube in the liquid line near the condenser outlet tube to meter refrigerant flow to the evaporator coil. To maintain minimum evaporator temperature and prevent evaporator freezing, a evaporator temperature sensor is used. The JTEC control module is programmed to respond to the evaporator temperature sensor input by cycling the air conditioning compressor clutch as necessary to optimize air conditioning system performance and to protect the system from evaporator freezing.