My buddy has a 2003 XLT 4x4 with the all red 3rd brake light. He wants to put the one with the two side lights... I was messin with it yesterday and noticed that the power wire for the two extra lights wast there. It has the same connector, but it only has two wire going to it, instead of three... is the third wire somewhere in the wiring harness or will I need to run the wire to it...

 

Mid-year 2003, Ford thrifted the cargo box light wiring from the roof harness. Yes, you can run a wire from the dimmer switch to turn on the lights or you can run from a dedicated aftermarket switch.

Many years ago, Rangers had the box lights tied to directly the dome light circuit and they would come on whenever the doors were opened.