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How to Install a Trailer Brake Controller: Complete Step-By-Step Guide

While many trucks designed for towing come with brake controllers built-in, there are still lots of times you need to add one. Most cars and SUVs do not have trailer wiring, so installing a trailer brake controller is important.

Luckily, the process isn’t nearly as complicated as you might think. However, this is one task you want to do right the first time. Today, we’ll walk you through how to install a trailer brake controller on your vehicle.

What You’ll Need:

1. The Correct Trailer Brake Controller: We wrote an extensive guide on selecting the right trailer brake controller that we recommend you read before getting started. You’ll need to consider the type and size of the trailers you’ll be hauling.

2. Tools: Once you’ve found a model that works with your vehicle and trailer, gather your tools. You’ll typically need basic tools like screwdrivers, wire strippers, pliers, and a socket set. Check the owner’s manual and instructions for your specific unit to see if it requires additional tools.

prodigy brake controller installed in motorhome
We have installed lots of brake controllers in our time on the road.

How To Install a Trailer Brake Controller

Once you’ve selected the trailer brake controller and gathered your tools, it’s time to start the installation. Remember, take your time completing this task. It’s an important job, and you don’t want to make any mistakes.

Step 1: Choose the Mounting Location

The first step in installing a trailer brake controller is to pick the mounting location. It needs to be in a convenient place for the driver to access when necessary without affecting their ability to drive. If it’s in the way, it could accidentally create a hazard. It needs to be accessible, however, so the driver can manually activate it.

In addition, remember to consider essential safety items like airbags. It could send your brake controller flying through the air like a projectile missile if it were to activate. Generally, the typical spot is to the right of the steering column, on or under the dashboard.

Lastly, the trailer brake controller most likely will need to be installed at a particular angle. Consult the controller’s materials to determine the correct angle for your controller.

Step 2: Connect Wiring

The next step will be to connect your trailer brake controller to your vehicle’s electrical system. Some automobiles make this more straightforward than others. If you’re lucky, you can use a wiring harness and connect it directly to your vehicle’s power. However, This only works if your vehicle has trailer wiring and a pre-installed brake line. Sometimes, you can use a partial harness to get power from your vehicle’s systems, but it will still require running a new wire to the back of the vehicle.

If you cannot get a wiring harness you will need to run new wires or tap existing. Because every vehicle and controller is different, the actual wiring is impossible for us to tell you how to do, but here are the basics. Let’s start with a diagram.

brake controller wiring diagram
This is the basic wiring for most electric brake controllers
  1. First, you need to power the controller (red wire in the diagram), which will also provide the power for the brakes so it needs to be robust. I always follow the manufacturer’s wiring recommendations, but I usually use 10 or 12-gauge wire for this purpose. Larger wire (10 GA) is best for 3-axle trailers. A fuse or breaker must also be added to the wire for safety. Breakers are preferred as they will automatically reset, which could be critical in a braking situation.
  2. Next, the controller will need to be grounded (Black Wire). This could be to the vehicle frame, but going back to the battery directly will guarantee the best connection.
  3. The controller also needs a signal from the vehicle’s brakes that it is stopping. This is usually a 12V signal that is taken from the existing brake switch. It is possible to add your own switch if needed and power it off your main line. Regardless of how it’s done, this signal tells the controller to start activating the trailer brakes.
  4. Lastly is the actual brake wire that will run back to the trailer plug (Blue). Blue is the standard color for trailer brake wire, but you can use whatever color you have available if you label it. Longer runs make the wire size larger as voltage drop is a real problem. I usually run 10 Gauge wire for this part.

If the above does not make sense to you or you feel overwhelmed, please consult a knowledgeable person with electrical skills to help. Brakes are not something you want to get wrong.

Suggested Reading: Learn tips for towing a trailer with our guide.

wiring for a trailer brake controller
Wiring for the brake controllers is always the hardest part. Because each vehicle is different, figuring out where to run the wires can be tricky. Note the simple 4 wires at the back of this controller (on the right)

Step 3: Mount the Controller

Once you connect the wiring, it’s time to mount the controller. You’ll want to place it in the spot you previously selected. Many controllers use velcro or other adhesives to keep it in place. Temporary options can be helpful if you rarely tow and don’t want it in the way.

If you’re looking for a more permanent solution, these devices often come with screws and the necessary hardware.

  1. Drill Mounting Holes – be careful not to drill into any electronics in the dash
  2. Install the Fasteners – be careful not to overtighten the screws

Step 4: Test the Connection

It’s time to test the connection with everything in place. Turn the device on and ensure it’s receiving power. Typically, these units have a power indicator light to help you know everything is ready. 

In addition, you’ll want to press on the brake pedal. Most models will have a light that activates whenever you press the pedal. This can help you confirm that the connection between the brake switch and controller works correctly.

You can also do a tug test with the trailer by pulling the manual activate lever and giving the vehicle a little throttle. You should feel the activated brakes pulling back on the vehicle.

shorted brakes error
Yikes, shorted brakes – that’s not good! This means there is something wrong in the wiring or trailer

Step 5: Adjust Settings

It’s time to adjust the settings if everything works as it should. Adjust the settings to match your towing requirements. We recommend starting on low and making some stops to see how it works. Don’t worry; you’ll fine-tune the settings later.

Step 6: Test Towing Operation

The next step is to hitch your trailer and test the towing operation. Ensure all your connections are secure and that you’re using safety features like chains. If something goes wrong, you’ll want to take the proper precautions.

With everything in place, take your trailer for a test drive. A large, empty parking lot is the perfect spot for this test drive. You should pay close attention when slowing down. You want to feel the trailer brakes assisting you with stopping.

Step 7: Fine-Tune Settings

One of the final steps is to fine-tune your settings. First, get up to approximately 25 miles per hour and squeeze the trailer brake. When everything works correctly, the trailer brakes should bring everything to a slow but firm stop.

If you notice it stopping too soon or too late, increase or decrease the sensitivity. It can take time to perfect everything, but you’ll be glad you did. It can help ensure your brakes last as long as possible.

Check Before Each Trip

Part of your pre-departure checklist should be to ensure your trailer brake is functioning correctly. Inspect the wiring and connections when hitching up. If you notice any damage, you’ll want to repair them as soon as possible.

Before pulling out, you’ll want to squeeze the trailer brake controller. You should feel the brakes engage and hold you and your vehicle in place. If you don’t, you’ll want to get out and inspect everything again to see if you can discover the problem.

Pro Tip: Knowing how to fix your trailer brakes will come in handy in a pinch.

How Electric Trailer Brakes Work

You Need a Trailer Brake Controller When Towing

A trailer brake controller is non-negotiable when towing. Many vehicles for towing will come with them from the factory. However, installing one is possible if your car doesn’t have one. These devices can help you and your loved ones stay safe while hauling your rig during your adventures.

Would you DIY a trailer brake controller installation? Share in the comments below.

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About Tom Morton

Tom, a Pacific Northwest native, is our technical genius. Born in Washington and raised in Alaska before settling in Michigan. He's the man who keeps our operation running, both figuratively and literally.

With a background in Electrical Engineering, Tom specializes in RV solar systems and lithium batteries. He made history as the first documented individual to use a Tesla battery module as an RV battery. Tom has personally assisted countless RVers with system installations and has educated thousands more through his videos and articles.

Cinematography is another of Tom's passions, showcased in his work on the Go North series. You can see his camera skills on display in The RVers TV show on Discovery Channel and PBS where he also stars as a co-host.

Tom's mechanical expertise extends beyond RVs to boats, planes, and all things mechanical. He's renowned for taking on maintenance and repair projects single-handedly and is often spotted underneath RVs, making him the technical backbone of our endeavors.

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Jeffrey Jessup

Wednesday 20th of December 2023

We pull our Rockwood 1940LTD with our Tesla Model Y. Even though the trailer is light enough to not require a controller and the regenerative braking does most if not all the stopping, I decided before even picking the trailer up from the dealer to install a controller. You just never know when a panic stop, blowout, or slick/hilly condition might make the added confidence of having a brake controller important. We purchased the tow package with the Model Y when new so it was not needed to run extra wiring to the back but I did have to get the correct pigtail from Tesla to tie into the wiring by the driver's footwell. The one thing I will mention also is that there isn't 12v provided to charge the house battery while towing but the solar on the trailer does that anyway. Thanks for a good article on the subject.