Operation

HEATER AND AIR CONDITIONER

The heating and A/C system pulls outside (ambient) air through the cowl opening at the base of the windshield and into the plenum chamber above the heating, ventilation and air conditioning (HVAC) housing, then through the A/C evaporator. Air flow can be directed either through, or around the heater core by adjusting the blend door with the temperature control knob on the A/C-heater control located in instrument panel. The air flow can then be directed out 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 heating-A/C system pulls outside (ambient) air through the fresh air intake 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 (Figure 1). Air flow is then directed either through or around the heater core. This is done by adjusting the position of the blend-air doors with the temperature controls located on the A/C-heater control in the instrument panel. The temperature controls use electric actuators to operated the blend-air doors. Air flow is then directed out the floor outlet, instrument panel outlet or the defroster outlet in various combinations by adjusting the position of the mode-air doors using the mode control located on the A/C-heater control. The mode control uses an electric actuator to operate the mode-air doors.

The fresh air intake can be shut off by selecting the Recirculation Mode using the A/C-heater control. This will operate the electrically actuated recirculation-air door, 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 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.






Figure 1 Typical Blend-Air Type HVAC System