For 1990-2009 cars

The base heater system is designed to provide heating, ventilation, windshield defrosting, side window defogging, and some vehicles, heating directly to the rear seat area.

The heater and fan assembly blower regulates the airflow 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 the air that passes through the heater core. The temperature door also controls the temperature of the air by controlling the mix of the heated air and the ambient air.

The mode door regulates the flow and the distribution of the processed air to the heater ducts and to the defroster ducts.

This console-mounted heating and ventilation panel contains the following:

1. The Rotary Temperature Control Knob

• | Actuates by cable.

• | Raises the temperature of the air entering the vehicle by rotation toward the right, or the red portion of the knob.

2. The Rotary Blower Control Knob

• | Turns on to operate the blower motor at four speeds.

• | Turns OFF to stop the blower.

• | Operates completely independently both from the mode control that regulates the defroster door and from the temperature control knob.

• | Changes the fan speed in any mode and at any temperature setting.

3. The Rotary Mode Control Knob

• | Actuates by electrical motor.

• | Regulates the air distribution between the windshield, the instrument panel, and the floor vents.

### The A/C Push Button

If the vehicle is equipped with air conditioning:

• | Controls the A/C.

• | Turns the A/C ON when the push knob is down. However, if the blower control knob is OFF, the A/C system is OFF, regardless of the position of the A/C knob.

### The Fresh Air Control

• | Operates by electrical motor.

• | Draws in outside air when knob is off.

• | Recirculates inside air when the knob is down and the indicator lamp is illuminated.

#### Airflow - Typical

#### Airflow with Rear Heating Duct (Left Hand Drive Shown, Right Hand Drive Similar)