1999 GMC Yukon Owner's Manual - Page 161

yellowblue Ventilation Tips Rear Window Defogger (If Equipped) If you see lines running across the rear window, you have a rear window defogger. The lines warm the glass. To turn on the rear window defogger, press this button next to the fan control knob. The rear window defogger will only work if the ignition switch is turned to RUN. For best results, first clear the window of as much snow or ice as possible. D Keep the hood and front air inlet free of ice, snow or any other obstruction (such as leaves). The heater and defroster will work far better, reducing the chance of fogging the inside of your windows. D When you enter a vehicle in cold weather, turn the blower fan to high for a few moments before driving. This helps clear the intake ducts of snow and moisture, and reduces the chance of fogging the inside of your windows. objects. This helps air to circulate throughout your vehicle. affect the performance of the heating and air conditioning system. D Keep the air path under the front seats clear of D The use of hood air deflectors may adversely Defogging and Defrosting On cool, humid days, use DEFOG to keep the windshield and side windows clear. Use DEFROST to remove fog or ice from the windshield in extremely humid or cold conditions. Use DEFROST with the temperature knob toward the red area and the fan control toward HI. The defogger will shut itself off after several minutes. If you need additional warming time, press the button again. You can turn the defogger off at any time by pressing the button. If your vehicle is equipped with the optional heated outside rearview mirrors, the rear window defogger button will activate the rear window defogger and the heated outside rearview mirrors. 3-9