8 Wire Boat Trailer Wiring to 5-Way Plug on Truck

Expert Reply:

There is not going to be a 5 flat that has 8 wires; the functions of the 8 wires are likely ground, running light circuit (split into 2 wires at the plug), left turn, right turn, brake lights (possibly split at the plug), and output to reverse lockout. What you will need to do is use a circuit tester such as # PTW2993 to determine the functions of the wires and wire them to 5-flat # A40W5B in the traditional manner of a 5-way which is ground, running lights, left turn/brake, right turn/brake and reverse electric lockout. I have added a link on trailer wiring which details the functions of the wires and how they normally connect for you to refer to.