Chevrolet 1998 Express Van Owner's Manual page 114

Interior Lamps
Dome Lamps
The dome lamps will come on when you open the doors.
You can also turn the dome lamps on by rotating the
thumbwheel, located next to the headlamp knob, all
the way up to the second notch. In this position, the
dome lamps will remain on whether the doors are open
or closed.
To use the dome override feature, push the button into
the "in" position. With the button in this position, the
dome lamps will remain off when the doors are open. To
return the lamps to automatic operation, push the button
and return it to the "out" position. With the button in this
position, the dome lamps will come on when you open
the doors.
Reading Lamps (Option)
You can use the DOME OVERRIDE button, located
below the headlamp knob, to set the dome lamps to
automatically come on when the doors are open, or to
remain off.
If your vehicle has reading lamps, press the button next
to the
lamp to turn
the lamp on.
Press the button again to turn the lamp off.
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