Buick 1994 Century Owner's Manual page 126

Press the ON portion of the switch. The indicator light
will glow. The rear window defogger will turn off
automatically after about 10 minutes of use. You can
also turn it off by turning off the ignition or pressing the
OFF portion of the switch.
I
NOTICE:
Don't use a razor blade or somerning else sharp
on the inside of the rear window. If you do, you
could cut or damage the warming grid, and the
repairs wouldn't be covered by your warranty.
Flow-Through Ventilation System
Your Buick's flow-through ventilation system supplies
outside air into the vehicle when it is moving. 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.
Keep the air path under the front seats clear of
objects. This helps air to circulate throughout your
vehicle.
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