Heating and Ventilation Systems

The base heater system is designed to provide heating, ventilation, windshield defrosting, and side window defogging. On some vehicles, it also provides heat directly to the rear seat area.
The heater and fan assembly blower regulates the air-flow from the air inlet for further processing and distribution.
The heater core transfers the heat from the engine coolant to the inlet air.
The temperature door regulates the amount of air that passes through the heater core. The temperature door also controls the temperature of air by controlling the mix of heated air with ambient air.
The mode door regulates the flow and the distribution of processed air to the heater ducts and to the defroster ducts.
The console-mounted heating and ventilation control panel contains three rotary control knobs and two push control knobs which operate as follows:

Rotary Temperature Control Knob
- Actuates by cable.
- Raises the temperature of air entering the vehicle by rotation toward the right, or the red portion of the knob.

Rotary Mode Control Knob
- Actuates by vacuum.
- Regulates the air distribution between the windshield, the instrument panel, and the floor vents.

Rotary Blower Control Knob
- Turns ON to operate the blower motor at four speeds.
- Turns OFF to stop the blower.
- Operates completely independently from both the mode control knob and the temperature control knob.
- Changes the fan speed in any mode and at any temperature setting.

Rear Window Defogger Push Knob
- Controls the rear window defogger.
- Turns On the rear window defogger when the push knob is pressed and illuminates the indicator lamp.

Fresh Air Control Push Knob
- Operates by vacuum.
- Switches between recirculating the passenger compartment air and bringing outside air into the passenger compartment.
- Is normally in the fresh air mode.
- Illuminates the indicator lamp when in the recirculating mode.