Automatic HVAC Description and Operation: Controller

The operation of the A/C system is controlled by the switches on the control head. This console-mounted heating and ventilation system consists of control knobs and a vacuum fluorescent display (VFD) indicating the status of the control settings selected.

Temperature Control Push Knobs

• Raise the temperature of the air entering the vehicle by turning the rotary switch clockwise (red arrow direction).
• Lower the temperature of the air entering the vehicle by turning the switch counterclockwise (blue arrow direction).
• Actuate the air mix door by an electric motor.
• Vary the mix of the air passing through the heater core with the air bypassing the core.
• Each press of a switch changes the set temperature by increments of 0.5°C (1°F). This is shown in the temperature window on the function display.

Vacuum Fluorescent Display (VFD)

• Temperature setting-Indicates the temperature set with temperature control knob.
• Auto status-Indicated whether the system is operating in the full automatic mode or manual mode.
• Defroster icon-Indicates manual selection of full defrost mode.
• Mode-Indicated by icon, the mode chosen by the system in auto (or by the operator in manual) is shown by an illumination arrow indicating the air path.
• A/C-A snowflake icon indicating whether the A/C is ON or OFF.
• Fan speed-Indicates the fan speed by illuminating a bar based on the segment at the front, for low speed, and adding additional segments in order up to the eighth, for high speed.

Seven Additional Push Knobs

• Full defrost-Causes the mode motors to direct all air to the windshield and aide window outlets for maximum defrosting.
• Air intake-Switches between fresh air intake, the default, and recirculating air. Airflow arrows on the display indicate the mode in effect.
• Full auto switch-Maintains the set temperature automatically. In this mode, the fully automatic temperature control (FATC) system controls the following:
  • The air mix door motor
  • The mode door motor
  • The blower motor speed
  • The inlet air door motor
  • A/C ON/OFF
• OFF switch-Turns the automatic air conditioning and fan control off.
• Mode switch-Allows manual selection of the airflow direction.
  • Selection is shown on the function display.
  • Each time the mode switch is pressed, the next function is displayed.
• A/C switch-Allows manual selection and control of the air conditioning function.
• Defogger switch-Turns ON the electric defogging heater in the rear window and the outside rearview mirrors, if the vehicle is equipped with heated mirrors.
• Fan control rotary knob-Allows for manual selection of the fan speed.