I rented an f-150 to tow some junk around while tow rig is fawked. Anyway 2005 f-150 with a easy plug in and a relay. So i hook up the brake controller to easy plug wires, and plug relay into fuse box. the easy plug has 5 wires one extra wire is a brown wire that says illumination something and from the diagram is tied to the headlight switch. anyways brake controller worked fine, brakes good, no problems and then as night fall came i turned on the lights and trailer brakes engage. I figured brown wire 5th wire was for a more advanced controller than mine that has a light and diplay and that is a seperate power source for it to come on with lights, but i am guessing i am wrong and this was a couse of my problemo. Anyone know what to do with this wire, or why it was doing it.