How To Wire Trailer Brakes? 7 Ways

If you are reading this post, it simply means you want to learn about different ways you can wire trailer brakes.

Having many wires with so many colors in your trailer isn’t fun when you try to change or install a new trailer light wiring due to a malfunctioning one or if you intend to have a new one.

Trailer wiring can be intimidating most at-times, but it shouldn’t be. Though you aren’t an electrician, that doesn’t imply that wiring a trailer is out of your scope or beyond your learning.

Perchance I will put you through on wiring the trailer yourself. It is valuable if you understand what each wire in your trailer wiring harness purpose, its destination, and if it is functioning correctly.

Nevertheless, this article will not only enhance your ability to install new wiring for your trailer, but it will also help you to explore the following contents; what is the color code for trailer wiring, the 7-way trailer plug color code, and how do you wire trailer lights and brakes, what is TM on trailer wiring, are all seven pin trailer connectors wired the same and more. Let’s begin right away!

What Is The Color Code For Trailer Wiring?

The color code for your trailer wiring is White, Yellow, Brown, Green, Blue, Red (or black), And Purple, but this color code depends on your electrical needs and the wiring on your trailer if it is 4, 5, or 7-pin flat connectors.

However, I will describe the color code for your trailer categorically. Just relax!

4-Pin Flat Connector

To start, the traditional trailer color code, which is a 4-pin connector for the consumer-type trailer, utility trailers, light boat trailers, little campers, and off-road trailers with lightweight and without brakes or power accessories, is below;

  1. White-Ground
  2. Brown–Tail Light
  3. Yellow –Left Turn Signal
  4. Green –Right Turn Signal

5-Pin Flat Connector

The 5-pin connector has an additional pin to that of the traditional trailer since it has brakes.

Then a blue wire is added to power the brakes. Similarly, for a 7-pin flat connector, two additional red and purple wires are added for auxiliary power and backup lights, respectively.

It is vital to note that no matter your trailer’s electrical systematics, use a compatible connector to your trailer.

7-Way Trailer Plug Color Code

Although knowing the color code for the 7-way trailer before commencing wiring is necessary, the process becomes easier for you. So far, the color code for 7-way trailer wiring varies according to different industries.

For SAE (Society of Automobile Engineers), standard wiring deviates from the RV standard wiring. Hold on to see the discrepancy and similarity below;

RV Standard

  • 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

SAE Standard

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

It is paramount to know that the minimum suggested size is 16 gauge for the turn signals, brake lights, running lights, and reverse light wires for a 7-way trailer plug.

Similarly, the minimum suggested size for the ground battery hot lead wires are 12 gauge for a 7-way plug.

How to Wire Trailer Brakes 7 Way

Since you are now familiar with the color code, let’s get into the step-by-step guide right away for your 7-way trailer brake;

Step 1- Prepare For Trailer Wiring

Ensure the required materials such as; a junction box for safety, a breakaway kit if your trailer disconnects, and a brake controller are ready.

Step 2 – Locate and Install the Junction Box

Suppose you intend to install a new junction box, though find a suitable location for installation at the edge of your trailer tongue.

The junction box should be close to the wires but away to avoid interference with other parts. Although, if you are replacing existing wiring, your trailer has a junction box.

Step 3- Make Trailer Connection

  • Having installed the junction box or if you had one already;
  • Remove old wiring, if any.
  • Remove the nuts on each junction box as you cut off about 5mm using a crimper of your new wire.
  • Place the ring terminals into each corresponding stud in the box junction box, such as (ground wire to the ground wire, brake to brake, and more).
  • Reinstall the nuts when you finish, though secure any excess wire with clips.

Note, if you are not using a junction box, connect the new 7-way to your already wiring system, as you can use a butt connector and heat gun to secure your wiring connections.

7-Way Trailer Wiring Diagram with Brakes

Here you can see a trailer wiring diagram for a 7-way connection with the brake.

How Do You Wire A 7-Pin Flat Trailer With Electric Brakes?

To wire a 7-pin flat trailer with electric brakes is simple using the procedures below. Let’s look at the tools you are required to have before you commence the steps;

The following tools will be very vital for easy and simple installation;

  • Wire Stripper
  • Philips Head Screwdriver
  • Cable Cutter

Instructional Procedure

Generally, this procedure is the same for all brands of the 7-pin plug.

  • Identify the type of 7-pin trailer plug you intend.
  • Strip the ends of your trailer cable by 5mm using a wire stripper.
  • Ensure that the wire ends do not strand as you twist them.
  • Unscrew the cap of the 7-pin plug.
  • Use a Philips Head Screw to lose the seven screws of the 7-pin plug but do not remove the screws.
  • Put the wire as appropriate as you match them and place them beneath the screws.
  • Replace the saddle device if your trailer has it, and tighten the screw for safety.
  • Hence replace the cable gland and trailer plug outer case as you tighten up carefully.

You are good to go as your 7-pin trailer plug is ready. Isn’t it simple!

Where Does The Brake Wire Go On A 7-Pin Trailer Plug?

The brake wire (blue for both SAE and RV standards) goes to the trailer’s brakes. The trailer’s brakes include the right turn /brake light and left turn/brake light since the blue is the brake power output.

Does A 7-Pin Trailer Plug Control Brakes?

Of course, it controls brakes since the difference between the 4-pin and 7-pins is the braking function. Thus, a 7-pin has a 12-volt circuit, a circuit for electric trailer brakes, and a reverse light (auxiliary power circuit). However, 5-pin and 6-pin trailer plugs do control brakes.

What Color Wire Is Ground On Trailer With Brakes?

Trailers that use brakes have 5, 6, and 7-pin plug systems. Hence, the color of the ground connection is white.

Although if you are connecting the wires from your trailer brakes, it is not necessary which wire you use for the brake feed or ground; the function magnet works either way.

Which Pin Is For Trailer Brakes?

If you use the 7-way plug or connector, the pin you will connect the brake output controller wire to be the 2-pin.

By description, the 2-pin will be at the 7 o’clock position from the inside (back) of your 7-way plug connector. Similarly, the 2-pin is at the 5 o’clock position when you look from the outside (front).

The wiring installation is the same for all brake controllers in a 7-way plug connector.

What Is S on Trailer Plug?

The S on a trailer plug represents the brakes on the 6-way plug wiring, which is blue. It is vital to note that the S is not available on the 5 and 7 trailer plugs.

How Do You Wire Trailer Lights And Brakes?

To wire your trailer lights and brakes requires you to follow the procedures;

Step 1: Install your plug cable in the trailer frame.

Step 2: Connect the green cable to the right turn signal of your trailer.

Step 3: Connect the yellow cable to the left turn signal of your trailer.

Step 4: You should connect the blue wire to your trailer brakes.

Step 5: Connect the brown cable to your trailer’s tail lights.

Step 6: Using a self-tapping screw, connect the white cable of the plug to the trailer frame.

Step 7: Splice all wires as you tap all connections. Simple right?

What Is TM On Trailer Wiring?

The TM on the trailer wiring represents Tail Light/markers/park lights for the brown wire. However, it is the tail/running light and right turn light in both SAE and RV standards.

Are All 7 Pin Trailer Connectors Wired The Same?

Indeed, the 7-pin trailer connectors or plugs are not the same. Don’t mistake grabbing any 7-pin plug you see and installing it in your trailer.

Although, there are mainly standards for 7-pin plugs: the SAE and RV wirings (blade and round pins). Hence the systematic setups have different colored wires; misconnecting them might lead to electrical issues.

Each blade or round pin connector has a deviation in the function of the connection port depending on the type of connector you intend to replace.

Perchance, the blade pin plug is standard in the fifth wheels, campers, and trailers, while round pin plugs are necessary for commercial and agricultural trailers.

What Color Is The Brake Controller Wire?

The color of the brake controller wire is blue wire. However, the blue carries the controller’s brake output for both SAE and RV standard trailer wiring for the 5, 6, and 7-way trailer wirings.

What Color Wire Is Brake Lights?

The brake lights have yellow and green for the SAE and brown and green wire colorsfor RV standards for a 7-way trailer wiring system. A 5-way trailer wiring has green and yellow for both right and left brake lights.

What Color Is Ground On 7 Pin Trailer?

On the 7-pin trailer wiring, the ground has white color. Though you should connect the white color wires (background) from each light and brakes or other accessories to the chassis of your trailer. So far, the minimum wire size is about 16 gauge.

How to Install Trailer Wiring Harness

Your trailer harness installation requires the simple steps below;

  • It would help if you positioned your plug at the front of your trailer so that harness can slack when connected to the trunk.
  • Attach the white wire to your trailer’s frame (ground)
  • Install the red/yellow cables along the left side of your trailer’s frame.
  • Install the brown/green along the right side of your trailer’s frame.
  • It would help if you connected the brown wire to each tail light.
  • It would be best to join the yellow wire to the left stop.
  • Connect the green wire to the right stop.
  • You should be combined the blue wire with the additional option.
  • Connect your harness plug to your trailer and turn on the headlights.

It is vital to note that the above steps are for the SAE and RV standards for installing the trailer wiring harness.


To sum up this post, it is not advisable to dive into a trailer wiring project blindly, though trailer wiring is very straightforward to work on if you have understood the detailed information.

That said, a 7-way RV plug or SAE plug diagram will help ensure that you are not connecting the wires back-to-back or matching them by colors but by functions to avoid electrical issues.

Be sure in the installation or wiring processes that the ground wire (white) is attached securely to the frame of your trailer side and should be large enough to withstand the entire load.

Hence, it is necessary to grease your trailer plug to prevent oxidation build-up. After wiring your trailer, ensure that you plug the two ends together and have a test run on the functionality of the wires.

Adjust as necessary; if the lights are up as they should, you are good to go.

I recommend you adhere to the instructions above for easy identification and installation of the 7-way plug for your trailer. Do like and share this informative article with others!

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