Ok what happens with backlit displays is this, When you turn on the parking lights (Which come on with the headlights) the dash lights DIM, this includes my Radio and several other indicators. THIS IS NORMAL.. In some cases you can "Cut" a wire (radio) to prevent it if you wish (I do not) but as others have said, Find the control and operate it. IF the headlight switch is a knob you pull. Turn it
If it's a Toggle or a rather special double toggle (mine is) there should be a nearby wheel and that's it.. Mine is not a ford however.