In this blog post, we will answer the following question: Do I need wiring for a hitch? We will explain how to install an electric harness by yourself in a few quick steps.

Do I need wiring for a hitch?

Yes, you need wiring for a hitch if you plan on towing a trailer or a camper. The wiring is responsible for connecting the brake lights, the running lights and the turn signals of your trailer. Wiring is thus mandatory.

Hitch wiring installation step-by-step

Although we recommend letting a professional install the wiring of your trailer hitch, it is possible to do it yourself. In this section, we explain how to do it by yourself.

Trailer hitches are always provided with the right connections, the right connections, the right lengths and thicknesses of cable to be installed in the vehicle. The user manuals shipped with each specific harness describe in detail how to perform this installation. Carefully follow the step-by-step plan:

Step 1 – Check the electrical circuits

Before starting the installation of a harness, you must first check that the electrical circuits of the vehicle to be equipped are functioning correctly. Check the operation of all the lights, and that there is no fault indicator illuminated on the instrument panel.

Step 2 – Note customer-specific settings

You have of course adjusted the settings to your own preferences. Just think of settings such as radio code, seat position and seat heating, when available on the vehicle. Write down all of these settings so that you can reset them to the correct position after installation.

Step 3 – Disconnect the battery from the vehicle

To work safely, it is necessary to disconnect the negative pole of the battery. This is to avoid disturbances when you make the electrical connection.

Note: Pay extra attention to disconnecting power from your car if you own a hybrid or electric car.

Step 4 – Check the preparation of the vehicle

Car manufacturers sometimes deliver their vehicles with and without coupling preparation. This is not visible from the outside.

Step 5 – Determine the passage of the wiring

The entry point for the wire harness is always indicated in the installation manual. This passage is usually located in the rear panel of the vehicle, thereby reducing the risk of water ingress to a minimum. The location of the point of entry is always prescribed by the automaker and in most cases has been prepared. In some cases, it is still necessary to drill. In this case, please treat the hole thus made with anticorrosive paint.

Step 6 – Wire the outlet

Wire the plug and install it on the bracket of your tow bar. When using a 13-pin receptacle, the first seven pins have the same function as the standard seven-pin receptacles. In the case of a 13-pin socket, your wiring harness is of course provided with the additional wiring which is necessary for the additional options of a 13-pin harness.

Step 7 – Pull the wiring

The wiring is installed in two positions. The first position is through the entry point in the back panel of your car. Via this entry point, you can pull the wiring towards the trunk. You have to be careful and precise.

If you pull the wiring too sharply, the metal of the vehicle can damage the wire harness strand. And your wiring will then be stripped. From the trunk, you will also need to pull the wiring to the front side of the vehicle. Please carefully remove the side panels inside your car.

Neatly conceal the wiring in the spaces behind the panels and ensure that the panels can be placed back in their original position. When installing the panels, be careful not to damage the wiring.

Step 8 – Trim removal set

The panels on your car are often installed with fragile clips. So please provide you with a trim removal set, including U-shaped and V-shaped levers. It is very easy to place them behind the clips, then you can easily and safely disassemble the inside.

Step 9 – Set up the wiring

With a return spring, it is easy to pull the cable from the back to the front. This saves time as you will not have to remove all the panels. Cable ties are useful for guiding the wiring. Be careful when attaching them. If you tighten them too much, the cable may break.

Step 10 – Establish the connection

The next step is to connect the harness to the vehicle. It is very important that you follow the instructions in the manual. Only then can you establish a secure connection without disruption. There are several ways to make connections.

Step 11 – Socket contacts

With some car manufacturers, it is fairly straightforward to use socket contacts (the connections at the end of a cable). You can simply add them in the desired and numbered position in the original connectors. Be careful because the contacts are sense sensitive. A bad connection can be made very quickly, but it is very easy to undo it by removing them with special extraction tools.

Step 12 – Electrical sleeve

In some cases, you have to cut a cable. You must then make a new connection by installing an electrical sleeve on the end of the wire. Using a crimping tool helps create the optimal connection.

Step 13 – Install only supplied hardware

In order to ensure correct installation and subsequently grant the warranty, it is very important to only use the parts supplied during installation.

Step 14 – Connect the grounds

When you have established the connections, you must then connect the ground points. Again, it is very important that you follow the instructions in the manual. Only then can you establish a secure connection without disruption.

Step 15 – Establish the connection to the 12V power supply

There are several ways you can make an electrical connection. For more modern vehicles, it is best to take power from the fuse box under the hood. For this option, Brink has developed specific fuse holders. This fuse holder can very easily be plugged into the fuse box where it takes the current necessary for the wiring harness.

Another way to make an electrical connection is to take power directly from the battery. However, this implies a subsequent check. Check if the battery does not drain and if this method does not disturb the memory circuits of your car.

Step 16 – Activate the hitch wiring

You may need to activate the wiring harness in the car after installation. Upon activation, the hitch is registered in the vehicle’s electronics, so all the electronics in your car can continue to function properly and adapt as soon as a trailer is hitched.

With universal diagnostic tools, you can activate most harnesses yourself. The following actions are then carried out: the deactivation of the reversing sensors, fog lights and lane assist, and activation of TSP, additional cooling and automatic gearbox.

Note: For certain types of cars, a dealer is the only one who can activate the wiring harness. There are also additional costs.

Step 17 – Check the wiring harness

Before you can use your car again, you need to perform a detailed check of the functionality of the installed wiring harness. There are several ways to perform this check.

Self-diagnosis function: Some of our specific electrical harnesses are equipped with a self-diagnostic function. After installation, the integrated module emits a red or green signal (led). Red means the installation was not successful, it must be redone. Green means you have successfully completed all of the steps. Thanks to the self-diagnosis function, you can always be sure that the installation of the wiring harness has been completed correctly.

Do not use pilot lights: For modern vehicles, the use of old-fashioned warning lights is not helpful. The same goes for small testers with led lamps. If your harness does not have automatic light control, it will be necessary to perform the test with two people.

After plugging your trailer plug into the plug, you yourself will need to get behind the wheel, plug in the ignition and control all of your car’s lighting functions. The other person should then check whether the taillights, brake lights, turn signals, fog lights, and reverse lights on your trailer are actually working.

Final advice

During the installation of your wiring harness, it is necessary to remove the interior trim. After a successful lighting check, please re-install them to their original location and check the interior parts for damage. Then test all the functions of your car, from the electric window controls to the adjustment of the exterior mirrors. Please finally reset all personal settings as you wrote them down before installing.

Do let us know if you have any questions or comments on the content.

FAQ on Do I need wiring for a hitch?

Where to connect the towing harness?

Depending on the age of your car, you can connect the tow bar in two different ways. For older cars, the current is transplanted directly to the taillights. For more recent cars, the connection is made at the location recommended by the manufacturer.

How to connect a 7 pin harness?

The connection is made to the wires supplying the rear lights of the vehicle. The wires of the harness must be transplanted to those of the vehicle corresponding to the desired function. The wires are never cut, just use the supplied quick connectors.

How to connect the wires of a trailer?

To connect the hitch plug, first pass the harness through the hole provided next to the hitch ball. Then, always refer to your trailer’s manual to find out how to connect the wires.

References

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Do I need wiring for a hitch?