Ford Mercury Villager 1997 Owner's Manual page 86

Interior Lamps
The front dome lamp is located overhead between the driver and
front passenger seats. However, if your vehicle is equipped
with a power sunroof, the dome lamp is located behind the driver's
seat.
The rear dome lamp is located overhead near the rear seating
positions.
The dome lamp switch positions
Either dome lamp will stay illuminated if the switch is pushed
to the ON position. The dome lamps will stay off if the switch is
pushed to the OFF position. When the switch is positioned to
the door/middle position, the dome lamps will come on when
either of the front doors or the sliding door is opened. The
front dome lamp, footwell lamps, and the sliding door step lamp
have a time delay feature and will gradually dim within about
15 seconds.
The rear dome lamp also illuminates when the liftgate is opened
and goes off when it is closed. However, the rear dome lamp
will not remain lit in the ON position unless the ignition switch
is in the ON position. This feature is intended to help avoid
a run-down battery which can occur when a light is left on
unintentionally.
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