Determining Wire Function On Boat Trailer With No Trailer Connector

Updated 08/10/2016 | Published 08/09/2016

Products Featured in This Question

7-Way Molded Trailer Wire Connector, 6' Long

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Deka Heat Shrink Butt Connector - 16-14 Gauge - Nylon Insulation - Blue - Qty 10

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$13.84

Hook Probe Circuit Tester

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$12.41

Wesbar 4-Pole Flat Connector w/ Jacketed Cable - Trailer End - 4' Long

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Question:

I bought a boat on wholesale, and only loose wires are hanging out of the trailer. The trailer per the registration is a 2007 Karavan, Model US-4100-SSB-78-ST-BLW. Do you have the correct parts so I can attach these loose wires to some type of plug? Id prefer to attach the wires to the most compliant plug, and the convert the plug with a converter down to a 4 flat which is what I will be using the majority of the time to pull the trailer. Can you help? Im trying to attach a picture of what I see coming out of the trailer, I have multiple pictures that I tried to attach but it looks like only one attached. Im not sure which one ended up getting attached. It looks like a set of yellow wires and a set of green wires, and two sets of brown and white wires with plugs. The Yellow and Green are loose hanging wires.

asked by: Brian K

Expert Reply:

It sounds like someone ran the wires as what we call a wishbone. The only way to tell how the wiring is connected to the lights is to use a 12V battery and a circuit tester like part # PTW2993.

Attach the white ground wire to the battery negative terminal and then one by one connect the other wires to the positive terminal. You can have someone watch the trailer lights while you do the testing to determine what function each wire carries. Depending on how many lights you have on the trailer you may find the wires are for marker or clearance lights on the side of the trailer that can be wired into the running light circuit. You can use butt connectors like part # DW05744-10 for the wiring.

Once you determine what each of the wires are for you can use a 4-way trailer wiring harness like part # W787264.

I have attached a helpful article about trailer wiring you can check out.

expert reply by: Jeffrey L