2003 GMC Sierra 1500 Pickup Owner's Manual - Page 178

Rear Window Defogger The lines you see on the rear window warm the glass. The rear window defogger uses a warming grid to remove fog from the rear window. (Rear): Press this button to turn the rear window defogger on or off. An indicator light in the button will come on to let you know that the rear window defogger is activated. The rear window defogger will automatically turn off several minutes after the button is pressed. Pressing the button while the defogger is running can also turn off the defogger. Outlet Adjustment r_ -r " . . If your vehicle is equipped with heated mirrors this button will activate them. Notice: Don't use anything 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. Donot attach a temporary vehicle license, tape, a decal or anything similar to the defogger grid. Use the air outlets located in the center and on the side of your instrument panel to direct the airflow. Your vehicle has air outlets that allow you to adjust the direction and amount of airflow inside the vehicle. Move the louvers up or down. Use the thumbwheel next to or underneath the outlet to close the louvers. For the most efficient airflow and temperature control, keep the outlet in the fully opened position. Rear seat outlets can be used to adjust airflow toward either seating area, the floor or upward. Move the center louvers up or down to direct the airflow. 3-23