How to Install a 7-Way Trailer Connector to Add a 12 Volt Power Lead to a Trailer

Question:

trailer has green and brown, yellow and brown,and a white want to put a 7 blade trailer end so i have 12 volt power Right is green and brown left is yellow and brown and white is ground do i put both browns together

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Expert Reply:

It sounds like you are missing a wire for the running lights on your trailer. Trailers that are wired for lights will have 4 or 5 wires, one for right stop/turn, one for left stop/turn, one for ground and one, possibly two, for running lights. Does your trailer have functioning turn signals, brake lights and running lights? If the two brown wires you mentioned are separate wires from the green and brown and yellow and brown wires, then you have a wishbone harness, which means you have a tail light wire for each side of the trailer. Those wires will connect to the same terminal inside the 7-way connector for the running lights.

When installing a 7-way trailer connector, you will need to cut off your current trailer connector and you can either connect your trailer wires to a 7-way connector like the Pollack 7-Pole Connector, # PK12706, or you can use a pre-wired 7-way connector like Hopkins 7-Way Molded Wire Connector, # H20042. It really depends on whether you want to wire the connector yourself or splice your existing wiring to the pre-wired connector.

Keep in mind, the wires coming from the Hopkins pre-wired connector do not use industry standard colors, so I attached a table that lists the functions of each wire.

To add a 12 volt power wire to your trailer, I recommend using an appropriate length of 10 gauge wire, # 10-1-1. You will need enough wire to run from the trailer connector to the items you will be powering.

If your tow vehicle does not have a 7-way connector, you can add one using the Curt 4 Pole and 7-Pole Adapter, # C57674. You can plug your existing 4-way trailer connector into the 4-flat connector from this adapter and simply run an additional power wire to the vehicle battery. You will use the black wire from this adapter for the 12 volt power wire. I recommend installing a 40-amp circuit breaker, # 9510, on this wire between the trailer connector and battery. This will protect your vehicle battery if something on your trailer draws an excessive amount of power.

Finally, I have attached a help article on trailer wiring for you to check out. This help article provides a basic trailer wiring diagram as well as tips on how to install and troubleshoot trailer wiring. If you have any further questions, feel free to email me.

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John H

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