Cant shut off headlights

I have a 99 chevy c1500 silverado (new body style). When it gets dark and the ignition is on, the headlights are on. They wont go off when the emergency brake is pressed, or by pressing the dome overide switch multiple times. Anyone got any ideas what I could check to turn off the lights, but leave the ignition on???

BEFORE YOU START YOUR TRUCK, PUT THE EMERGENCY BRAKE ON, THEN TURN YOUR TRUCK ON,LIGHTS WILL BE OFF