Chevrolet 2003 Impala Owner's Manual page 103

Automatic Dimming Rearview Mirror
Your vehicle may be equipped with an automatic
dimming rearview mirror. Push the button in the center
of the mirror to turn this feature on. The mirror will
darken gradually to reduce glare from headlamps behind
you. This may take a few moments. The mirror will
lighten whenever you shift to REVERSE (R).
There are two lamps located on the bottom of the
mirror. Each lamp is turned on and off by pressing the
button next to the lamp.
One photocell on the front of the mirror senses when it
is becoming dark outside. Another photocell, facing
rearward, senses headlamps behind you. To turn the
automatic dimming feature off, press the button in
the center of the mirror again.
To keep the photocells operating well, occasionally
clean them with a cotton swab and glass cleaner.
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