Why Do My Trailer Brakes Lock Up In Reverse? (Troubleshooting Trailer Brakes Controller)

Why Do My Trailer Brakes Lock Up In Reverse

Are your trailer brakes locking up when you reverse? Wondering what is causing the problem? Well, we have a couple of reasons why your trailer brakes may be locking up.

Before we dive into this information, I do want to point out that there are dozens upon dozens of reasons why a set of brakes may lock up when you are reversing.

Some of them may be specific to the type of vehicle or trailer that you are using. It may even be related to the specific brake controller that you are using.

As a result, I am not able to go through every potential reason why brakes would lock up here. It would be tens of thousands of words.

So, why do your trailer brakes lock up in reverse? Below you can find some of the most common reasons why do your trailer brakes lock up in reverse:

  1. Brake Gain Too High
  2. Short on the 7-Way Trailer Connector
  3. Loose Bolts
  4. Surge Brakes in Trailer
  5. Broken Pins in Plug
  6. Fuse
  7. Faulty Brake Controller

What is a Brake Lock-Up?

Perhaps the best way to describe a brake lock-up is when the brake force at stopping a tire from moving is greater than that of the stopping force that the road is able to provide.

If this happens, then the wheel will stop turning completely. It will stop dead in its tracks.

Obviously, if a wheel stops turning completely, you aren’t going anywhere. The tires will be struggling to get anywhere. This places an extreme amount of pressure on the tires, which can cause damage. You won’t be reversing either.

Brake lock-ups are not a good thing. Well, for the most. This is why it is good to get to the bottom of why they are occurring in the first place.

Read also: Should Electric Trailer Brakes Lock Up? (Explained)

Want to Deal with a Brake Lock-Up Quickly?

While this isn’t really going to help you with your problem in the long-term, we know that there are some people that just want to park their vehicle and be done with it.

If you are trying to park, then you can disconnect the brakes. If the brakes are disconnected, then the brakes will not work.

Yes. This is a rather crude situation, and it may actually be illegal in your state depending on the amount of weight in the trailer.

However, it almost certainly is going to be the quickest method for dealing with brakes locking up. You can work out why they were locking up later on.

Read also: What Is The Average Cost To Install Trailer Brake Controller – (Facts & Numbers)

Brake Gain Too High

If you don’t know what the gain is, it is the amount of pressure that the brakes apply to the trailer. As we mentioned before, a brake lock-up occurs when there is more pressure being applied by the brakes than the road.

Therefore, if your gain is too high, your brakes will lock-up.

If you have a lighter trailer, then the gain will need to be lower. This is because the lighter trailer will need to have far less force applied to it to help it stop.

Your brake controller will allow you to adjust the gain. Switch it down and it may stop the brakes from locking up when you reverse.

If you do not know how to adjust the gain, then consult the instruction manual for your brake controller as it will vary from model to model.

Read also: Tekonsha Wireless Brake Controller: 11 Facts You Should Know (Explained)

Short on the 7-Way Trailer Connector 

Sometimes there can be a short on the 7-way trailer connector i.e. the small socket on the back of the vehicle where the electronics are plugged into.

The main things you want to look out for here are the purple connector. This is the brake light and the blue connector. That is the blue connector.

What happens is that, sometimes, the wire from either of these gets a little bit frayed or, for whatever reason, makes contact with the other wire. They are virtually opposite each other on the socket, so it is to be expected.

When they get frayed, the brake light will short out the brake output. This creates a short circuit and the brakes will lock up.

You can diagnose this problem yourself. You will have to test the brake output connection when the vehicle is in reverse using a circuit tester.

However, this can be dangerous unless you have some way to block off the wheel. After all, you do not want a vehicle backing over you!

If you suspect this is the problem, and it is likely is if the vehicle seems to have the problem every time you reverse, then get in touch with a mechanic to diagnose the problem.

Alternatively, you can look for any fraying or potential short circuit issues yourself.

Read also: If My Trailer Has Electric Brakes Do I Need A Brake Controller? (Explained)

Loose Bolts

This is rarer, but it can happen. The more the brakes get used, the more things can end up being knocked loose. Sometimes it may be wise to check over the brakes to ensure that nothing has come loose, even a small amount.

If it is has, then you just have tighten things up.

This may cut down on a significant number of braking issues.

Surge Brakes in Trailer

This is going to be dependent on the type of trailer that you own. Some of them will have something known as ‘surge brakes’ in them.

These are meant to protect you from brake locking when you reverse. However, sometimes there can be faulty wiring which causes the reverse to happen.

This isn’t really a problem that you can deal with yourself, so you may want to have an expert look at your trailer to see what the problem is.

Read also: Curt Wireless Brake Controller: 9 Facts You Should Know (Explained)

Broken Pins in Plug

Sometimes the problem can be as simple as a broken pin in the plugs (we already covered the sockets). Check the plugs for both the brake/electric system for your trailer. You should also check the plug for the brake controller that you have installed.

Sometimes, it is going to be pretty obvious if a pin is bent or damaged. While you may be able to bend the pin back into place if the damage is only minor, we recommend that you try and replace the entire plug instead.

They should be fairly easy to wire up. You just need to make sure that you get the wiring right. The last thing that you want to have happen is more wiring issues, right?


This is a problem specific to some models of vehicle. However, there are some cars (including Ford and Chevrolet vehicles) that have a small fuse under their hood. If this fuse blows, then the brakes do not disengage properly when you are reversing.

Of course, this is going to cause brake lock-ups.

The fuse will be under the hood, so keep an eye out for any burned-out fuses there. interestingly, you would never know that this fuse is related to the braking system at all. It is just a random fuse. 

Faulty Brake Controller 

This is an exceedingly rare problem because most brake controllers are fairly tough and there isn’t really a lot that can go wrong with them. However, it is still worth checking out if the other methods haven’t really solved the problem.

As you may well know, the job of the brake controller is to tell the electric brakes on the trailer when they should be engaging.

It does this by keeping an eye on your vehicle’s brakes for whatever reason. Now, sometimes, the brake controller can break.

If the brake controller is telling the trailer to brake when you are not actually braking, then the wheels are going to lock up.

Almost all brake controllers will have some sort of diagnostic option, or at least an indicator that tells you when the trailer brakes are being applied by the system. This means that you will want to keep an eye on that. If the brakes are being applied and you are not actually braking, then you may have an issue with that controller.

Obviously, the only way that you could probably deal with this problem is replacing the entire controller. There may be some fixes that you can find online. however, a lot of these are only going to be temporary.

If your brake controller has got to the point where it has issues telling brakes to disengage, then it is going to be untrustworthy. After all, you need the braking system of the trailer to be working properly when you are out there on the road. It is unsafe otherwise.

Electric Trailer Brake Diagnosis & Repair >> Check out the video below:

Best Trailer Brake Controller

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Conclusion Troubleshooting Trailer Brakes Controller

As you can see, there are plenty of reasons why brakes may lock up. As we said at the start, it is impossible for us to cover all of the reasons why it is happening.

If your brakes are locking up for a reason that isn’t specified here, then we do urge you to search for your vehicle online.

Some vehicles, especially Ford Trucks, are known for having brakes lock up when they reverse. There are guides on how you can deal with this.

There may also be guides on ensuring that your vehicle’s trailer brake controller also works properly i.e. through small adjustments.

Remember, it is in your best interests to solve this problem quickly.



Mike Gilmour

Hi, I'm Mike, co-founder, and editor of RV and Playa. My passion is traveling (with my RV) and enjoying the day at the beach (Playa)! Well, I originally created this blog as a way to share what I've learned by experimenting with the RV lifestyle, and I want to help others develop in life through new skills and opportunities.

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