2003 GMC Savana Van Owner's Manual - Page 143

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. Turn the knob on the right of the climate control panel to select the defog or defrost mode. Rear Window Defogger Press this button to turn the rear window defogger on or off. Be sure to clear as much snow from the window as possible. The rear window defogger uses a warming grid to remove fog or frost from the rear window and will only work when the ignition is RUN. The rear window defogger will turn off several minutes after the button is pressed. If turned on again, the defogger will run for several more minutes before turning off. The defogger can also be turned off by pressing the button again or by turning off the engine. Notices 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 defogger and the repairs would not be covered by your warranty. Do not attach a temporary vehicle license, tape, a decal or anything similar to the defogger grid. +3 (Blend): With this setting, the outside air comes out of both the floor and defroster outlets. Adjust the temperature knob for warmer or cooler air. The air conditioning compressor may operate in this setting to dehumidify the air. 9(Defrost): This setting operates the defroster. Most of the air comes out near the windshield, with some going to the floor outlets and front side windows. The air conditioning compressor may operate in this setting to dehumidify the air. The blend setting is useful for cold weather with a large number of passengers or very humid conditions to help keep the windshield clear. Use defrost to remove fog or ice from the windshield quickly in extremely cold conditions. The temperature knob should be in the red area and the fan control toward high. Do not drive the vehicle until all the windows are clean. 3-22