1994 GMC Sonoma Owner's Manual - Page 116

Comfort Controk Flow-Through Ventilation System Your vehicle's flow-through ventilation system supplies outside air to the inside of your vehicle when it is moving. With the side windows closed, air will flow into front air inlet grilles,through the vehicle, and out the rear the air exhaustvalve. Outside air will also enter the vehicle when the heater or the air conditioning fan running. is Ventilation Tips Keep the hood and front air inlet free ice, snow, or any other of obstruction (such as leaves). The heater and defroster will work far better, reducing the chanceof fogging the insideof 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 ductsof snow and moisture, and reduces the chance of fogging the inside of your windows. Keep the airpath under the front seats clear objects. This helps air to of circulate throughout your vehicle.