How To Hardwire A 4-Way Harness On A Small Utility Trailer

Question:

I have a simple trailer with no brakes and just running lights. Break/turn signal lights on the back and reflective lights on the side. There are a total of 7 wires, 3 sets of 2 and then a white by itself. I need to hook these wires up to a 4 wire connector. What is the proper method?

asked by: Joel A

Expert Reply:

In order to wire a 4-way harness onto your trailer, you will need a few simple items. The first of which will include our Deka Heat Shrink Butt Connector part # DW05744-10 and the Electrical Connector Dielectric Grease part # LT37534. The rest of the tools needed for this install should be fairly common in most toolboxes.

Before you install the wires, you will need to strip back a 1/4" of the jacket from each wire and place them into opposite ends of the butt connector. After you have done so you will need to use a pair of wire crimpers or pliers to secure the wires to the connector. Once the connection has been made, wiggle the wires around the plug to ensure they will not come loose. After you have done these steps you can take a torch or lighter and seal the ends of the connector to the wire itself.

The white wire coming from the back of the 4-way will need to be grounded to bare metal on the trailers frame. The next wire you will hook up is the yellow wire responsible for the left turn/brake light. Attach this wire to the left turn/brake light wire coming from the trailers wiring harness. I strongly recommend testing the wires before splicing as there isn't an industry standard color code. Next you will attach the green wire responsible for the right turn/ brake light. The last wire you will need to run is responsible for the tail lights. Attach the brown wire from the back of the 4-way to your trailer's wiring harness with that function.

If you do not have a manual for the trailer that will instruct you as to which color wire represents which function, you will need to connect a 12 V battery and check the individual wires with a circuit tester like part # PTW2993.

The additional wires you are seeing represent other various functions the trailer is capable of. For example, reverse lights and brake controllers. If you wish to wire these additional wires into your harness you will need the Adapter 4 Pole to 7 Pole Vehicle End Trailer Connector part # 30717.

For a wishbone wiring harness, the running light is split at the trailer connector eliminating the need for a jumper wire across each tail light. The yellow/brown wire designated the drivers side running light whereas, the green/brown represents the passenger running light. To do this you will need the Wishbone 4-Way Trailer Wiring Harness part # A20WB.