How To Do 4 Pin & 7 Way Trailer Plug Wiring Diagram with Brakes

Last updated on January 12th, 2023 at 09:31 am

Suppose you have had a trailer for some time but have issues wiring it. It is the right time to replace your trailer plug if you need help figuring out where to start.

It is a little bit of a complex task to do. Although, having the right skills will help you have the upper hand as you begin wiring a 7-way plug on your trailer using a mix of the video below, the 7-pin trailer wiring diagram with brakes and battery here in this article, and descriptive text for each process,

7 way trailer plug wiring diagram

A 7-way plug connects power to a trailer when towing. You would also need your trailer to have a signal when you are turning or braking; thus, the connections made through this 7-way plug on the trailer make it possible.

On the other hand, all makes and models of the 7 way plugs are designed differently, so you need a repair manual that could include wiring diagrams for each model. Similarly, the models of the 7-way plug wiring include; the SAE and RV standard wiring.

7 way trailer plug wiring diagram

This guide will address and provide solutions to the following typical queries ranging from; what do the colors mean on a 7 way trailer plug, are all 7 pin trailer connectors wired the same, how do you wire a 7 way plug on a trailer, 7 way trailer plug wiring diagram, what color wire goes where on a 7 pin trailer plug, and more.

How do you wire a 7-way plug on a trailer?

What Do The Colors Mean On A 7-Way Trailer Plug?

A 7-way trailer plug’s color code is vital before you commence wiring. Good knowledge of color will make the wiring easier. 

Check out what colors mean in the SAE and RV wiring standards.

RV Standard Color Code

  • Green–Tail Lights
  • Yellow – Reverse Lights
  • Brown – Brake Light/Right Turn Signal
  • White–Ground Wire
  • Blue – Output Brake Controller
  • Black – Battery Hot Lead
  • Red – Brake Light/Left Turn
What do the colors mean on a 7-way trailer plug?

SAE (Society of Automobile Engineers) Standard Color Codes

  • Purple – Reverse Lights
  • Black – Battery Hot Lead
  • Blue – Output Brake Controller
  • White–Ground Wire
  • Brown–Tail Lights
  • Yellow – Brake Light/Left Turn Signal
  • Green – Brake Light/Right Turn Signal

Are All 7 Pin Trailer Connectors Wired The Same?

Of course, not! All 7-pin trailer connectors are different in wiring models and make. However, there are varying standards for 7-pin connectors; the RV and SAE wirings with blade and round connectors which is the one I will focus on here.

The two systematic setups differ in colors and design. So both blade and round connectors deviate in function and depend on the port you are wiring. 

The round connectors are designed for agricultural and commercial trailers, whereas the blade connectors are the standard in campers, travel trailers, and the fifth wheels. 

I suggest you find the specific connector on your 7-pin trailer rather than pick anyone available. Although, misconnection might lead to electrical issues.

What do the colors mean on a 7-way trailer plug?

How Do You Wire A 7-Way Plug On A Trailer? And Trailer Wiring Diagram 4 Pin

Let’s start with a step-by-step guide since you are familiar with the color codes.

Tools needed

  • A Screwdriver
  • A butt connector
  • Heat gun
  • Wire clips
  • Crimper

On the Trailer Side

Step 1: Prepare To Wire A Trailer

Provide necessary materials such as a breakaway kit, a junction box, and others.

Step 2: Locate And Install The Junction Box

Install the junction box at the edge of the trailer tongue if you replace the existing one. And it should be a little far from the wires to avoid interference with other parts.

7 pin trailer plug wiring diagram usa4

Step 3: Make The Trailer Connection

  • Pull off the old wiring.
  • Pull out each nut on the junction box using a screwdriver.
  • Use a crimper to cut about 2 to 5mm off your new wire.
  • Place the terminals in each corresponding stud in the junction box.
  • Replace the nuts, tighten them, and secure any excess wire with clips.

Note: Use a butt connector and heat gun to secure your wirings if you are not using the junction box system for your 7-way plug on your trailer.

On The Vehicle Side

  • Plug the trailer-end connector into your vehicle-end connector. Then, you are ready to roll.

Trailer Wiring Diagram 4 Pin

For a trailer wiring diagram 4 pin type, please  check out the trailer diagram for 4-pin below;

What do the colors mean on a 7-way trailer plug?

7 Way Trailer Plug Wiring Diagram with brakes

Indeed, a diagram is essential for successful wiring. So, do check out the 7-way plug wiring diagram for your trailers  with brakes below:

What Color Wire Goes Where On A 7-Pin Trailer Plug?

The tables below will guide you to where each color wire goes in a 7-pin trailer plug. And you may also need to refer to the image above for paring the wire color appropriately.

RV Standard

Wire ColorFunctionWhere To Attach(Vehicle Side)Where To Attach(Trailer Side)Wire Gauge
Green Tail/Running Lights.Right turnRight Turn Signal        16
Yellow Reverse LightsLeft Turn.Left Turn Signal.        16
Brown Brake LightsTail LightTail Lights        16
WhiteGround wireVehicle ground point – uncoated metal.Trailer ground point – uncoated metal.        12
BlueOutput Brake ControllerElectric Brake Control Power OutputTailer’s brakes        12
BlackBattery Hot LeadBack-up Circuit of vehicle’s wiring harnessBack-up lights/hydraulic coupler.        16
Red Brake LightsFused Battery lead or Fuse block.Breakaway kit/battery charger or interior lights.        12

SAE Standard

Are all 7 pin trailer connectors wired the same?
Wire ColorFunctionWhere to Attach(Vehicle Side)Where to Attach(Trailer Side)Wire Gauge
Purple Reverse lightsBack-up Circuit of vehicle’s wiring harnessBack-up lights/hydraulic coupler.      16
Black Battery Hot LeadFused Battery lead or Fuse block.Breakaway kit/battery charger or interior lights.      12
Blue Output Brake ControllerElectric Brake Control Power OutputTailer’s brakes      12
WhiteGround WireVehicle ground point – uncoated metal.Trailer ground point – uncoated metal.      12
BrownTail/Running LightsTail LightTail Lights      16
YellowBrake LightsLeft Turn.Left Turn Signal.      16
Green Brake LightsRight turnRight, Turn Signal.      16

 Watch this video on how to wire a trailer plug


 Where does red wire go on 7-way trailer plug?

 In most cases, the red wire on a 7 Way trailer wiring or connector harness is for brake light and left turn signal functions. However, some wiring harnesses may have a yellow wire for brake and left turn lights. Just reconfirm that with your manual.  For instance, with the  Pollak 7 Way connector wiring, the red wire is for brake light and left turn signal functions, as well as many others. 


In my final words, there is nothing as intimidating as having several wires on a 7-way trailer plug when looking at it from the outside. However, trailer wiring can be straightforward if you are familiar with the systematic color codes of both the RV and SAE standards.

A 7-way trailer wiring diagram would be helpful to ensure that you don’t connect the wires by matching them by colors. 

But instead by function to avoid electrical issues. I recommend the use of butts and heat guns other than junction boxes. 

Ensure that you have a test run of the installation process, and make adjustments if necessary.

So far, the detailed work above should be helpful for easy identification and installation of a 7 way plug on your trailer. Do well to share this write-up with others!

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