GMC 1995 Jimmy Owner's Manual page 138

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.
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.
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.
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Keep the air path under the front seats clear of objects. This helps air to
circulate throughout your vehicle.
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