4 pin trailer wiring installation

4 pin trailer wiring installation

A 4 pin trailer wiring is frequently used by common light-duty trailers, including many utility and boat trailers, to connect to the towing vehicle. The necessary running lights, turn signals, and brake lights are provided for the trailer through this link. Additionally, a pin for a ground wire is supplied.

You must match the wire colors and attach the ground wire to the frame in order to complete the wiring installation. Some installation tasks must be carried out from the trailer side, while others must be done from the vehicle side. Before you get on the road, remember to test the connection. Well in this article we’ll be discussing the 4 pin trailer installation and some other related questions.

4 pin trailer wiring installation


  • What are the 4-Way Trailing Wiring Color Codes?
  • What are the supplies and tools needed for a 4 pin trailer installation
  • How do you install a 4 pin trailer wiring?
  • What to do when finished?

So, let’s begin!


What are the 4-Way Trailing Wiring Color Codes?

The meanings of each color must first be understood before you begin the installation. While certain manufacturers’ codes may differ slightly from one another, most of them employ the same generic options.

  • White: Ground wire
  • Brown: Tail/running lights
  • Yellow: Left turn/brake light
  • Green: Right turn/brake light

Before connecting any wires to your car, make sure they all work by checking the owner’s manual or using a circuit tester. The circuit tester is often located in the rear of the vehicle, behind the taillights, and can be used to access the wiring system of your vehicle. To ensure you have the correct wire, turn on each function (turn signals, brake lights, etc.) in turn and look for a corresponding signal from the circuit tester.

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What are the supplies and tools needed for a 4 pin trailer installation

The followings are the tools and supplies needed for a successful 4 pin trailer installation;

  • 4-pin wiring kit (green, yellow, brown, and white wires)
  • Crimping tool combo with a cutter and stripper
  • Waterproof butt connector with heat shrink ends
  • Heat gun
  • Zip ties
  • Plastic wire tubing
  • Terminal connector
  • Power drill and small drill bit

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How do you install a 4 pin trailer wiring?

Below is the step by steps process for a successful 4 pin trailer wiring;

Prepare for Trailer Wiring Installation

  • Make sure you have all the necessary supplies on hand before beginning. To make sure everything is there, I advise using a trailer lighting kit.
  • Take inventory before you begin if you are only changing a few connections and wiring pieces. Determine which components can be kept and which must be replaced.

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Connect Ground to Trailer Frame

  • A clean, bare area of the trailer frame must be used as the connection point for the ground wire. The connection will be made using a self-tapping screw and ring terminal. Pick a spot on the ground that is free of pollution, rust, and paint. Clean it off first if you must.
  • 2-3 feet to be added to the trailer hookup past the tongue. Make sure there isn’t any paint, corrosion, or accumulation near the ground. (Clean if required.) Make the ground connection on the main frame of the trailer, behind the tongue, if the trailer folds.

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  • Run the remaining wires to the taillights along the trailer frame. Avoid letting the wires chafe or catch on any trailer parts.
  • The cables should be run via the trailer frame’s hollow areas. Grommets can be installed by drilling into the frame if necessary. When dealing with loose wires, zip ties, and wire clips are also beneficial.

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Install Vehicle Side Wiring

  • It’s time to concentrate on the vehicle once the trailer is linked. You are prepared to go if your car has a 4-way connector already. The vehicle’s trailer side can be plugged in to start towing.
  • It is simple to add a 4-way connector to your car if it doesn’t already have one. The make and model of your car will determine the connector type you use.

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Connect Trailer with Vehicle

  • The cables can now be connected to the vehicle. You can remove the wires’ insulation with your crimper. The wires can be securely connected using a butt connection and a heat gun.
  • Another option is to split the running light into two wires using a Y (wishbone) harness. The trailer has two sides, one of which runs along the driver’s side and the other along the passenger side.
  • You will utilize the same grounding procedures on the car as you did on the trailer. Make sure the ground wire is attached to a frame surface that is bare, clean, and metal. You can also apply dielectric grease if you wish to stop corrosion.
  • The lighting components of the car are where the wiring harness will clamp or plugin. The power line from the electrical harness should not be run to the car’s battery because otherwise, your lights will always be on.

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Test Connection

  • When everything is finished, you are prepared to test the connections. While you observe from behind, ask a friend to assist you in turning on all of the lights.
  • Before you drive the trailer, make sure all of the lights are operational. Otherwise, you run the risk of endangering yourself or being stopped by the police.

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What to do when finished?

It’s a good idea to plug the two ends of your trailer and car together after wiring them both, then test the operation of each wire. Make necessary alterations. You’re fine to go if everything lights up when it should!

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4 pin trailer wiring FAQs

What are the wires for a 4 pin trailer?

For the right turn signal, use green. The left turn signal color is yellow. The ground is white, and the taillights of the trailer are brown. The combination of these four different wire types is referred described as “four-way wiring.” The majority of light-duty trailers and boat trailers can be equipped with four-way wiring, which is relatively common.

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What is the difference between 4 pin and 5 pin trailer wiring?

A four-pin connector, which manages the turn signals, brake lights, and taillights, is all about lighting. If you upgrade to a five-pin trailer wiring connector, depending on the plug, you can install electric brakes or reverse lights.

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What is the red wire on a 4 pin trailer plug?

If the right turn signal side, the red wire serving as the turn signal will be connected to the harness’s green wire, and the black wire to the brown wire.6 Mar 2012

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What is the 4th wire for electrical?

The equipment grounding conductor is the fourth wire in that cord and plugs combination. The missing wire in the older 3-wire systems is the equipment grounding circuit. Two hot wires and one neutral wire made up the wiring in these older appliance installations where 3-wire connections could be connected legally.

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What is an auxiliary wire on the trailer?

An auxiliary circuit connects the tow vehicle’s battery to the trailer plug on the back of the van through a circuit breaker. It will usually connect to the second pin of the socket and work with the caravan’s normal wiring.

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How is a trailer wired?

The left-side turn signal and brake light are powered by the yellow wire. The right-hand turn signal, brake, and light are all controlled by a green wire. In a typical four-wire arrangement, the white last wire serves as the ground.

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Howhow does 4 wire trailer lights work?

For the security of your car, while towing, the majority of utility trailers run on a 4-pin trailer plug. For the 4-pin connector, the right turn/brakes are on the green wire, the left turn/brakes are on the yellow wire, the taillights are on the brown wire, and the ground is on the white wire.

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What is a 4 pin cable?

This harness can connect to the majority of common trailer wires thanks to its 4-pin plug. Its 16-gauge wire is ideal for connecting to taillights, brake lights, and turn signals. This adaptable item is the ideal switch for your outdated wiring harness.

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That’s all for this article where we discussed the steps involved in a 4 pin trailer installation, where we also answered the following questions related to it;

  • What are the 4-Way Trailing Wiring Color Codes?
  • What are the supplies and tools needed for a 4 pin trailer installation
  • How do you install a 4 pin trailer wiring?
  • What to do when finished?

I hope it was helpful, if so, kindly share. Thanks for reading.