How to Wire a 7-Pin Trailer Plug: Step-by-step Guide

We've all experienced it - you arrive at your destination, go to unhook your trailer, only to find that the trailer plug has slipped out on the journey and been compromised, or the wiring has worn out due to running on the ground.

While you can take the trailer to the mechanic to replace the connectors, it is much more cost-effective (and satisfying!) to do it yourself. Keep reading for a step-by-step guide on how to fix your trailer wiring.

Why Choose a 7-Pin Trailer Plug

A 7-pin trailer plug has the benefit of additional pins, which can be used for additional lights on your trailer. They also have wiring for electric brakes, which is important when towing a heavier trailer such as an RV or boat trailer.

7-pin trailer wiring can also allow for a source of 12 voltage power on your trailer, which can be useful when you have a utility trailer that needs the ability to charge various work machinery.

Types Of 7-Pin Trailer Plugs

7-pin trailer plugs can come with either round pins or flat pins. The round pins are quite uncommon, and you're more likely to see a connector with flat pins on modern vehicles. There are different shapes of plugs, which we have explained below:

7 Pin Small Round Trailer Plug

The small round 7-pin trailer plug is used for lightweight trailers. It is an older design of trailer wiring but is still widely used. It can also be used for a light utility trailer or a light boat trailer.

7 Pin Flat Trailer Plug

This type of trailer plug is mostly seen on newer SUVs and trucks that come with pre-installed trailer wiring. Some of these connectors have LEDs that light up when the proper connection is made, making it easy to see if you have connected the trailer plug correctly. This version of trailer wiring is very easy to connect, causing it to rise in popularity.

Seven-Pin Large Round Trailer Plug

This style of trailer plug is used for heavy-duty towing, such as agricultural and commercial trailers. The pins in this plug are bigger than those in its smaller counterpart, and the wiring is done differently. When using these plugs, using the correct cable gauge for your trailer wiring is important.

Color Code Variations Of Seven-Pin Trailer Plug Wiring

When wiring your trailer plug, it is crucial to have a color code diagram to assist you in connecting the wires to the correct pins. These trailer wiring diagrams differ depending on what you are towing, so make sure to use the correct diagram for your trailer. Please see the trailer wiring diagrams listed below for more information on wiring your trailer connector.

SAE Traditional Trailer Wiring Diagram

Image Credit: etrailer.com

  • White = Ground
  • Brown = Running Lights
  • Yellow = Left Turn Signal & Braking lights
  • Green = Right Turn Signal & Braking lights
  • Blue = Electric Brakes
  • Black or red = 12v Power
  • Brown = Auxiliary / Backup Lights

RV Standard Trailer Wiring Diagram

Image Credit: etrailer.com

Follow this color code when wiring your trailer:

  • White = Ground
  • Brown = Right Turn and brake lights
  • Yellow = Reverse lights
  • Green = Tail lights / Running Lights
  • Blue = Electric Brakes
  • Black = 12v Power
  • Red = Left Turn and brake lights

Heavy Duty Trailer Wiring Diagram

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  • How to Wire a 7-Pin Trailer Plug: Step-by-step Guide. Tow Ratings. Retrieved from http://towratings.net/blog/how-to-wire-a-7-pin-trailer-plug-step-by-step-guide/.