1996 GMC Suburban Owner's Manual - Page 140

.. . .. . I 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 of fogging the inside of your windows. ..> .._...i s i When you enter a vehicle in cold weather, turn me blower fan t o HI 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. Keep the air path under the front seats clear of objects. This helps air to circulate throughout your vehicle. . . . Your vehicle has air outlets in the center and on the sides of your instrument panel. You can move the outlets from side to side orup and down to direct the flow of air, or close the outlets altogether. When you close an outlet, it will increase the flow of air coming out of any outlets that are open.These outlets do not completely shut off airflow when in a closed vent position. 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. 3-8