2006 Cadillac STS Owner's Manual - Page 194

Recirculation is not available in the defrost mode and will shut off when defog mode is selected. Both of these features are designed to limit fogging in your vehicle. If recirculation is selected during defog mode, it will automatically turn off after 10 minutes to limit problems with fogging. In some conditions, using recirculation for long periods of time may cause the air inside your vehicle to become too dry or stuffy. To prevent this from happening, after the air in your vehicle has cooled, select AUTO to return to automatic climate control operation or push the recirculation button again to select outside air. Pressing this button a second time selects outside air. exhaust fumes from older, poorly running or diesel-equipped vehicles that are driving near you. This sensor, when active, will monitor the air quality in front of your vehicle and switch to air recirculation when poor quality air is detected outside your vehicle. You can activate the air quality sensor on your vehicle (if equipped) by pressing the AUTO button on your climate control. The word AUTO will be shown in the center of the climate control display under the outline shape of a vehicle. When the air quality sensor senses poor quality air, the recirculation graphic will be shown as long as the sensor senses poor quality air. Under some conditions, the air quality sensor system will not operate. In cold weather, the system may not be active (even if the AUTO indication is displayed) because of concerns of fogging your windows, which may occur by activating recirculation mode. Also, the air quality sensor system will not remain in recirculation mode for extended periods of time that could cause stuffy or very dry conditions in the vehicle. Following a poorly running vehicle for an extended period of time may not keep recirculation active indefinitely. : (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 may be equipped with an optional air quality sensor to help limit the climate control system from pulling in some harmful 3-50