Automotive trailers are electrically wired as an extension of the automotive electrical system. Smaller trailers are generally wired for the basic signals—brake lights, turn signals and marker lamps. Larger trailers, on the other hand, are often wired with trailer brakes, separate turn-signal and stop lamps and auxiliary power. To enable these extra features, a more complex 6-way or 7-way wiring system is needed.
In particular, a 7-way wiring system provides not only the signal lighting system, but also a means by which to charge a 12-volt battery.
Cut a length of black wire. Strip one end of 1/2 inch of insulation, and connect to one of the battery terminal connectors. Solder this connection. Loosen the battery terminal retaining bolt, and install the battery terminal to the positive (+) battery post. Tighten the battery terminal bolt so that the connection to the battery is snug.
Cut a length of white wire, and strip one end of 1/2 inch of insulation. Connect this wire to the other battery terminal, and solder the connection. Loosen the battery terminal retaining bolt, and install the battery terminal to the negative (-) battery post. Tighten the battery terminal bolt as in Step 1.
Place one wire splice connector on the trailer black wire. Insert the battery black wire into the splice connector connection hole. Crimp the wire splice connector until the metal blade is flush with the plastic case.
Place the second wire splice connector on the trailer white wire. Insert the battery white wire into the splice connector connection hole. Crimp the splice connector as in Step 3.
Connect the trailer plug to the automobile trailer wiring socket.
