2009 Chevrolet Silverado 2500 HD Extended Cab Owner's Manual - Page 218

Rear Window Defogger The rear window defogger uses a warming grid to remove fog from the rear window. Sensors The solar sensor, located in the defrost grille, in the middle of the instrument panel, monitors the solar heat. Do not cover the solar sensor or the system will not work properly. < (Rear Window Defogger): For vehicles with this feature, press to turn the defogger on or off. It automatically turns off several minutes after it has been activated. The defogger can also be turned off by turning the engine off. Do not drive the vehicle until all the windows are clear. 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. Heated Mirrors: For vehicles with heated outside rearview mirrors, the mirrors heat to help clear fog or frost from the surface of the mirror when the rear window defog button is pressed. See Outside Power Mirrors on page 2-59. The interior temperature sensor, located in the headliner, measures the temperature of the air inside the vehicle. There is also an exterior temperature sensor located behind the front grille. This sensor reads the outside air temperature and helps maintain the temperature inside the vehicle. Any cover on the front of the vehicle could cause a false reading in the displayed temperature. 3-32