1997 GMC Safari Owner's Manual - Page 114

Dome OverrideButton Reading Lamps (Option) You may have the optional reading lamps next to the dome lamps. Turn the lamps on and off by pressing the switch next to the lamp. You can adjust the lamps to any desired position by rotating the lamp and they will work when the ignition is on or off. Be sure to turn the lamps off before you leave the vehicle. If the DOME OVERRIDE button is out, your interior lamps will work as usual. If the button is pressed in, the interior lamps will not come on when any of the vehicle's doors are open. The button is located next to the lamp switch. If you have the optional reading lamps, they will still operate if the button is pressed in. 2-40