Operation
OPERATION
Both the manual temperature control (MTC) heating-A/C system and the heater-only system 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. The temperature control determines the discharge air temperature by operating the blend-air door. This design allows almost immediate control of output air temperature.
NOTE: Typical blend-air type HVAC system shown.
The 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 when equipped with A/C, 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 (3) with the temperature control 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 cables 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.
When equipped with A/C, 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.
When equipped with A/C, 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 directs air to the inside base of the windshield through the outlet located in the top center of the instrument panel. The defroster outlet receives airflow from the HVAC housing through the molded plastic defroster duct, which is secured to the instrument panel top. 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 demisters direct air to the front side windows through outlets located on the top corners of the instrument panel. The demister outlets receive airflow from the HVAC housing through the defroster duct and two molded plastic demister ducts. 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 top cover. The demisters operate when the mode control is anywhere between floor and defrost settings. Some air may be noticeable from the demister outlets when the mode control is in the bi-level to floor positions.
The left and right panel outlets receive airflow from the HVAC housing through a molded plastic air distribution duct and the center air outlets directs airflow from the distribution duct to the two center panel outlets. The airflow from each of the panel outlets is adjustable by rotating the outlet in any direction.
The front and rear floor outlets receive airflow from the HVAC housing through the floor distribution ducts. The molded plastic ducts direct airflow to the front foot wells and beneath the carpet on both sides of the center tunnel to the rear outlets. None of the floor outlets can be adjusted.