Chevrolet 1995 Astro Cargo Owner's Manual page 123

You can turn the defogger off at
any
time by pressing the bottom of the switch.
The defogger will shut itself off after several minutes so that the glass does not
get
too hot.
If
the window still isn't clear, turn the defogger on again.
NOTICE:
Scraping the inside of your rear window could cut and damage
the defogger. Your warranty would not cover this damage. And
don't put decals there, you might have to scrape them off.
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 at the base of the windshield, through the vehicle
and out the rear air exhaust valves. Outside air will also enter the vehicle
when the heater or the air conditioning fan is running.
Venfilation 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.
0
When you enter a vehicle in cold weather, turn the blower fan
to
HIGH for a
few moments before driving off. This helps clear the intake ducts of snow and
moisture, and reduces the change
of fogging the inside of your windows.
0
Keep the air path under the front seats clear of objects. This helps air to
circulate throughout your vehicle.
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