I have bought a 2004 fe450 and am looking for a wiring diagram , I am wanting to get rid of the ign barrel and just need to know what the 4 wires do, I have 2 yellows, a brown and black with yellow trace, one of the yellows goes live when staring and is live while running, I take it the brown is an earth but don’t know about the black/yellow, also the rear light and brake light isn’t working