1995 GMC Yukon Owner's Manual - Page 168

You can turn the defogger off at any time by pressing the button again. The defogger will shut itself off after several minutes, so that the glass does not get too hot. If the defogger shuts off, and the window still isn't clear, turn on the defogger again. Ventilation System Your vehicle's ventilation system supplies outside air to the inside of your vehicle when it is moving. With the side windows closed, air will flow into the front air inlet grilles, through the vehicle, and out the rear air exhaust valve. Outside air will also enter the vehicle when the heater or the air conditioning fan is running, unless you have the recirculation button pushed in. For more information see "Recirculation Button" in this section. Ventilation Tips 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 0.f fogging the inside of your windows. When you enter a vehicle in cold weather, turn the blower fan to HI for a few moments before driving off. This helps clear the intake ducts of snow and moisture, and reduces the chance of fogging the inside of your windows. 0 Keep the air path under the front seats clearof objects. This helps air to circulate throughout your vehicle. Some models also have vents under the front seats. Keep the area at the outlet grills clearof floor mats or other objects. This will ensure proper air flow to the rear floor area. 3-8