2001 Chevrolet Impala Owner's Manual - Page 177

Rear Window Defogger Press the button marked REAR to turn the defogger on. An indicator on the button will light. The rear window defogger and the mirrors will automatically turn off after about 15 minutes. If you turn them on again, the defogger and the mirrors will only stay on for about seven and one half minutes before turning off again. You can also turn them off by turning the ignition off or by pressing the button again. Do not attach anything like a temporary vehicle license or decal across the defogger grid. NOTICE: Don't use a razor blade or something else sharp on the inside of the rear window. If you do, you could cut or damage the warming grid, and the repairs wouldn't be covered by your warranty. Don't put decals there because you might have to scrape them off. When turned on, the rear window defogger uses a warming grid to remove fog from the rear window. If your vehicle has the optional heated outside mirrors, they will heat to clear the mirror surface before driving. 3-7