1997 GMC Suburban Owner's Manual - Page 159

Ventilation Tips Keep the hood and front air inlet free ice, snow or of any other obstruction (such as leaves). Theheater and defroster will work far better, reducing the chance of fogging the inside your windows. of When you enter a vehicle in cold weather, turn the blower fanto HI for a few moments before driving. This helps clear intake ducts of snow and the moisture, and reduces the chance fogging the of inside of your windows. Keep the air path under the front seats clear of objects. Thishelps air to circulatethroughout your vehicle. Your vehicle has air outlets the centerand on the sides in of your instrument panel.You can move the outlets from side to side orup and down to direct the flow air, or of close the outlets altogether. When you close an outlet, it will increase the flow air coming out any outlets of of that are open. These outlets do completely shut off not airflow when in a closed position. vent The use of hood air deflectors may adversely affect the performance of the heating and air conditioning system. 3-9