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Although the specific details for wiring will be included with the trailer manual, the basic procedure for wiring connectors is the same for most trailers. If you require to hitch up a new trailer or replace/maintain an existing trailer light wiring then this guide will provide you with the information to get the job done quickly whether it is a new installation or maintenance work on existing wiring.

Allow around 2-3 hours for the entire process (up to 4 hours for boat trailer wiring), but make sure you have all the tools and equipment required before starting out to avoid delays.

Cable Routing

A trailer hitch wiring harness to suit all applications should be easily sourced from online retailers, be aware of the color variances described below, and consider ordering additional small items as described below for the best possible finish.

Take some time to plan your trailer light wiring routing to avoid frustrating issues later. Have some cable ties ready of differing lengths, and look for opportunities to hide the cabling away. Also, consider purchasing a mounting bracket to attach it to the vehicle. This not only presents a tidy job, but eliminates risk of the wiring becoming damaged. It may be possible to feed the cables through the trailer box beam or tubing, or use a short length of plastic duct to shield the wiring from the elements.

One tip to watch for if you do feed the wires through trailer box sections or tubing, is to be aware of low spots that can potentially hold water in wet conditions. This could cause electrical issues resulting with incorrect signals being displayed, or no signal at all. Water ingress is an especially important consideration for boat trailer wiring.

Cable Coloring

Trailer Wiring Connectors for 4, 5, 6 and 7-way pins

Trailer Wiring Connectors for 4, 5, 6 and 7-way

In our guide below we list the most common coloring schemes for trailer wiring connectors, with one or two deviations from these schemes. Different manufacturers can stray from these normal colors so always check the handbook, or use a circuit tester to identify the wiring.

For quick reference note the major manufacturers deviations from standards are shown below:

  • GMC sometimes use a black ground cable and a pink brake cable
  • Ford are known to use orange for right turn, and green for left turn and red for brake lights
  • Chrysler use Brown for right turn, and green for left with a white brake wire
  • Jeep have a grey left turn, blue for tail lights and blue/black stripe for brakes
  • Toyota use green wires for the turn signals with a yellow stripe for right and black for left
  • Honda use black for ground and stripes for other wires
  • Mazda also use striped wires with a red stripe for brakes and a solid black for ground

4 way wiring

4 way connectors can come as a flat connector, or a round connector. The most commonly used wiring for trailers is a 4 wire connector, using a standard male/female connection.

For safety reasons, it is normal for the male connector to come from the trailer, and the tow vehicle to have the female connector. You will note that one of the four pins on the male connector is actually a female post, and vice versa on the other side – this is the ground pole and will be colored white.

The color scheme for a 4 pin is shown below:

Wire Color Wire Usage
Green Right Turn and Stop lights
Yellow Left Turn and Stop lights
Brown Running lights, tail lights and license plate
White Ground

Here’s a quick tip to help you remember the left and the right.

  • gReen is for Right
  • yeLlow is for Left

5 way wiring

A 5 way is also available as a flat or round connector, but in addition to the 4 way it has an additional pin that is usually for disconnecting the hydraulic coupler during reversing.

6 way wiring

If your trailer set-up has electric brakes or capacity for a 12v supply, you’ll be looking for a 6 way wiring system.

It would be nice to have consistency; however, a 6 way is the opposite of a 4 way because the male plug on a 6 way is on the tow vehicle side. You can immediately identify the vehicle side plug as it has a hinged cover to protect the male prongs.

The coloring system should be the same as a 4 way, with two additional color’s, as follows:

Wire Color Wire Usage
Green Right Turn and Stop lights
Yellow Left Turn and Stop lights
Brown Running lights, tail lights and license plate
Blue Electric Brakes
Red 12v supply
White Ground

Sometimes the 12v supply is colored black, please check carefully!

6 way trailer connectors are sometimes square, but more usually round.

7 Way

A 7 way wiring is the same as the 6 way described above, but has an additional connection that can be used to run 12v electrics in a RV, for example light circuits. This is known as the auxiliary feed and is usually colored orange or sometimes purple. In a 7 pin connector, it is usual to locate the aux in the middle of the connector.

Resolving Wiring Issues

So, you have wired up your trailer with the trailer hitch wiring harness, checked all the connections, switched on the vehicle and found there are no lights. Now you have some trouble shooting to do.

Trouble shooting trailer wiring connectors and wiring problems can be difficult if it is not undertaken in a systematic manner, so follow our guide and you’ll be up and running in no time!

For no lights functioning at all either upon new installation, or after a period of time…

  1. Check 12v power wire is connected to tow vehicle battery
  2. Check/ replace fuses and relays
  3. Check ground connection
  4. Check harness rating is suitable for loading

Additionally, a 12v probe circuit tester can be used to check for supply at the plug.

In 90% of cases, one of the above will be the cause of trailer light wiring issues.