1998 GMC Sonoma Owner's Manual - Page 135

Ventilation System For mild outside temperatures when little heating or cooling is needed, use VENT to direct outside air through your vehicle. Airflow is through the instrument panel outlets. You can direct the airflow side-to-side by rotating the thumbwheel located in the center of the vent. The vent can be tilted up and down also. To control the amount of airflow through the outlets, rotate the thumbwheel below the vent. Your vehicle's ventilation system supplies outside airto the inside of your vehicle when it is moving. When the vehicle is not moving, you can get outside air to flow through by selecting any mode and any fan speed. Ventilation Tips 0 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. When you enter a vehicle in cold weather, move the fan control to high 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. Keep the air path under the front seats clear of objects. This helps air to circulate throughout your vehicle. 0 0 Defogging and Defrosting On cool, humid days, use BLEND to keep the windshield and side windows clear. Use DEFROST to remove fog or ice from the windshield quickly in extreme humid or cold conditions. Turn the temperature knob to the right and move the fan control toward high. You will find air outlets in the center and on the sides of your instrument panel. 3-5