2005 Dodge Dakota, Headunit Dimmer Wire

I have a head unit that provides for a dimmer display if you turn on your headlights, but there are no instructions as to how to wire it. I see on the pinout diagram that there is an orange wire for "dimmer" and a black/yellow for "illumination." Should I connect to one of these (which one?), or to the headlight wire that's active when the lights are on, and if the latter, which wire is it, and where do I find it besides at the switch itself? The way the unit works is there are separate brightness settings for when your lights are on or off. When it detects your headlights are on, it activates the "night" setting in the unit. Thanks!DougieD

The black/yellow is fine....same lead as parking/tail lights. Be sure to insulate the orange wire.