2008 Cadillac STS Owner's Manual - Page 207

If there is fogging on the side windows, remain in defog or defrost mode until they clear. 0 (Defrost): Press this button to direct most of the air to the windshield, with some air directed to the side windows and outboard panel outlets. In this mode, the system automatically turns off recirculation and runs the air-conditioning compressor, unless the outside temperature is at or below freezing. Recirculation cannot be selected while in the defrost mode. This mode can also cause the fan speed and air temperature to increase. = (Rear Window Defogger): Press this button to turn the rear window defogger on or off. Be sure to clear as much snow from the rear window as possible. The rear window defogger turns off about 10 minutes after the button is pressed. If the vehicle's speed is above 30 mph (48 km/h), the rear defogger stays on continuously. If turned on again, the defogger only runs for about five minutes before turning off. The defogger can also be turned off by pressing the button again or by turning off the engine. The heated outside rearview mirrors also heat to help clear fog or frost from the surface of the mirror when the rear window defogger is on. See Outside Power Heated Mirrors on page 2-43. Notice: Do not use a razor blade or sharp object to clear the inside rear window. Do not adhere anything to the defogger grid lines in the rear glass. These actions may damage the rear defogger. Repairs would not be covered by your warranty. Rear Window Defogger The rear window defogger uses a warming grid to remove fog or frost from the rear window. The rear window defogger only works when the ignition is on or during remote start, if programmed. See "Personal Settings Menu" under Vehicle Personalization on page 2-60 for additional information. 3-53