2008 Cadillac STS Owner's Manual - Page 204

The mode switch can also be used to select the defog mode. Information on defogging and defrosting can be found later in this section. yAz (Fan): Press this switch to increase or decrease the fan speed. Pressing this switch cancels automatic operation and allows the operator to manually select the amount of airflow. Press AUTO to return to automatic operation. If the airflow seems low when the fan speed is at the highest setting, the passenger compartment air filter may need to be replaced. For more information, see Passenger Compartment Air Filter on page 3-55 and Scheduled Maintenance on page 6-4. In some conditions, using recirculation for long periods of time can cause the air inside the vehicle to become too dry or stuffy. To prevent this from happening, after the air in the vehicle has cooled, select AUTO to return to automatic climate control operation or push the recirculation button again to select outside air. Press this button a second time to select outside air. : (Outside Air): This mode forces the system to pull air from outside the vehicle. It can be used to bring fresh air into the vehicle. Air Quality Sensor: Your vehicle could have an air quality sensor to help limit the climate control system from pulling in some harmful exhaust fumes from older, poorly running, or diesel-equipped vehicles that are driving near you. This sensor, when active, monitors the air quality in front of your vehicle and switches to air recirculation when poor quality air is detected outside your vehicle. Press the AUTO button on the climate control to activate the air quality sensor. The word AUTO comes on the center of the climate control display. While the air quality sensor senses poor quality air, the recirculation graphic displays. h (Recirculation): Press this button to control the air source for the climate control system. If in AUTO mode, press this button once to select recirculation. This mode keeps outside air from coming in the vehicle and recirculates the air in the vehicle. It can be used to prevent outside air and odors from entering the vehicle or to help cool the air inside the vehicle more quickly. Recirculation is not available in the defrost mode and shuts off when defog mode is selected. Both of these features are designed to limit fogging in the vehicle. If recirculation is selected during defog mode, it automatically turns off after 10 minutes to limit problems with fogging. 3-50