Mercury 1996 Grand Marquis Manual page 108

Do not put any articles on top of the photocell
that is located in the top left corner of the
instrument panel. This photocell controls the
autolamp. If you cover it, the photocell reacts as
if it is nighttime, and the lamps turn on.
You can adjust the autolamp to keep the lamps
on after you leave your vehicle. The further you
move the headlamp knob to the left
(counterclockwise), the longer the lamps stay on.
You can set the autolamp so the lamps stay on
for up to three minutes after you turn your
vehicle off.
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