2008 Buick Lucerne Owner's Manual - Page 167

Defogging and Defrosting Fog on the inside of windows is a result of high humidity (moisture) condensing on the cool window glass. This can be minimized if the climate control system is used properly. There are two modes to clear fog from your windshield, defog and defrost. Rear Window Defogger The rear window defogger uses a warming grid to remove fog or frost from the rear window. < (Rear Defogger): W (Floor/Defog): Use this mode to clear the windows of fog or moisture and to warm the passengers. Turning the control to this mode directs about half of the air to the floor outlets and the remaining air is directed to the side window outlets and to the windshield. When this mode is selected, the system turns off recirculation and runs the air-conditioning compressor unless the outside temperature is at or below freezing. The recirculation mode cannot be selected while in the floor/defog mode. 0 (Defrost): Use this mode to remove fog or frost from the windshield more quickly. Turning the control to this mode directs most of the air to the windshield and the side window 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. Press this button to turn the rear window defogger on or off. An indicator light below the button comes on to show that the rear window defogger is activated. Be sure to clear as much snow from the rear window as possible. The rear window defogger will only work when the ignition is in ON/RUN. The rear window defogger stays on for about 20 minutes after the button is pressed if you are traveling at slower vehicle speeds. At higher vehicle speeds the rear window defogger may stay on continuously. If turned on again, the defogger only runs for about 10 minutes before turning off. The defogger can be turned off by pressing the button again, by turning the ignition to ACC/ACCESSORY or ON/RUN, or by turning off the engine. The heated outside rearview mirrors will heat to help clear fog or frost from the surface of the mirror when the rear window defogger is on. See Outside Automatic Dimming Heated Mirror on page 2-38 for more information. 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. 3-29