Why Are My Trailer Brakes Locked Up When Plugged In?

My trailer brakes locked up when plugged in, what could be the issue? There could be several problems – your brake controller may not be in the correct position, or your brake might have failed. Let us look at the reasons.

If you are experiencing the electric brakes on the trailer locking up when you plug it in. Then this problem could be because of several reasons. While traveling in a trailer, you want to be sure that the brakes on your trailer work fine for your safety, your family’s safety, and the protection of all your stuff. 

When you experience the brakes not working correctly, many things will run through your mind. This article will cover some of these things in detail further. 

Trailer Brakes Locked Up When Plugged In

Why Are My Trailer Brakes Locking Up? 

There can be some reasons for the trailer brakes of your trailer to be locking up. The brake controller on your trailer might be adjusted incorrectly according to the load on the trailer. You need to adjust the brake controller according to the load. 

Another reason could also be brake failure, and the trailer brakes might be locking up due to a mechanical or technical failure in the brakes. Excessive grease on the brake’s shoes is also a factor responsible for the locking up of the brakes. 

Semi-Trailer Brakes Lock Up When Empty.

  • The brakes on your semi-trailer brakes lock up when it is empty because of some issue in the primary ground wire. If the main ground wire and the magnet ground wires are not attached properly, you’ll find that the brakes will lock up. 
  • As most people cover more considerable distances in a trailer, the trailer must have all the safety measures covered. This also includes the trailer brakes. Faulty or broken connections among the wires could be the primary reasons the trailer brakes lock up. 
  • The primary ground wire should be connected to a clean, bare metal surface. At the same time, you can also check the brakes for any visible corrosion, wear, tear, rust, and dents in the wiring. 


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Trailer Brakes Engage When Plugged In

  • You’ll need to figure out first whether your trailer uses a 6-way trailer connector or a 7-way trailer connector. One of the possible reasons for the trailer brakes is when you plug it into the vehicle, as you can use the wrong adapter. 
  • The difference in the wiring can engage the brakes immediately. There are mainly two methods for wiring by which a person can wire a trailer connector. One method requires a center pin as the brake voltage for the output circuit. The second way requires a center pin for the auxiliary circuit. 
  • If you have wired the truck one way and the adapter in another way, the trailer brakes will engage immediately as soon as you plug them in. This will happen because the 12-volt power is fed directly to the trailer’s brakes. To confirm the voltage was reaching the brakes, you can use a circuit tester. 

Trailer Brakes Locked Up When Plugged In

Trailer Brakes Locked Up When Unplugged

After ensuring that the trailer brakes and all the wiring are secure and connected correctly, you need to check the power wires. Wires with damage and wear and tear can be responsible for the trailer brakes locking up when unplugged. 

Again, you can use a circuit tester to test the power reaching the brakes. The reading on the circuit tester should be positive. With this circuit tester, you can also check by turning the headlights. The headlights and the turn signals should not give a positive sign when your brakes are applied. 

Where To Set The Fifth Wheel On A Semi-Trailer? 

Ideally, the fifth wheel on a semi-trailer should always be located at the central line of the back tandem or at the front of the axle on the rear wheel. You should identify the fifth wheel on the semi-trailer ideally because of the following reasons:-

  • Load distribution:- The fifth tire or wheel should be placed where the load of the trailer and the tractor is evenly distributed. If the weight on the wheel is not evenly distributed on the wheel, there is a high percentage chance of the wheel popping out. 
  • Steering:- The fifth wheel should also be connected to the other wheels so that there is no disturbance while you are driving the trailer. The best position for the fifth wheel is either the rear axle of the trailer or the centerline of the rear. 
  • Avoid damage to the sleeper: In installing the fifth wheel, you should not damage the integrity of the sleeper area on the trailer. There are some cases where people accidentally damage the trailer while using a fifth wheel. 
  • Avoid damage to the trailer:- Don’t damage the trailer by using a fifth wheel. Always take help from a professional to install a fifth wheel on your trailer. 

Why Are My Trailer Brakes Smoking? 

Overheating can happen in the brakes for a variety of reasons. There could be something stuck or damaged to the truck’s braking system. If you hit something on the road, this could also damage your braking system. Your trailer brakes can smoke for a lot of reasons. 

A faulty braking system puts you and other drivers on the road at risk. You can prevent this problem by regularly maintaining your braking system. Smoke from the braking system is usually because of overheating. 

In some severe cases overheating can also result in your trailer catching fire. The best way to protect yourself and the trailer is to stop the trailer as soon as you observe the smoke. You can then perform an inspection to check what the issue is with your trailer. 

When I Reverse My Trailer, Why Do My Brakes Lock Up? 

Your trailer brakes would lock up while reversing if a hydraulic coupler is present on the trailer. These hydraulic brakes will remain locked up until you connect the trailer connector with the couplers lock-out circuit. 


You might like to read: Brake Lights won’t Work When Headlights Are On


Frequently Asked Questions

How do you unlock trailer surge brakes?

According to the manual, you should release the brakes by turning a knob present on the tongue of the trailer. You can also place a key in the slot, and this key will prevent your trailer from power surges on the brakes. 

Power surges on the brakes could also be because of some fault in the connections or the wiring systems. If the trailer is wired in one way and you wire it another way, there will be compatibility issues. 

Trailer Brakes Locked Up When Plugged In

What would cause trailer brakes not to release?

There could be a lot of reasons for the trailer brakes not to release. If the brake controller is not calibrated correctly or does not receive the ideal power levels, the brakes won’t release.

This scenario most likely relates to your braking system generating a braking signal when you are not applying any pressure or pressing the brakes. A short-circuit on the vehicle’s and trailer’s connector can also be responsible for the trailer brakes not being released. 

A Few Final Words

Trailer brakes lock while plugging them in, mainly due to faults in the trailer’s wiring and the braking system. If there is some residue or damage to the braking system, then your trailer will lose its braking power. 

You need to take this braking issue very seriously, as it could put your life at risk. Instead of doing things yourself, it would be better if you take professional help. 

Thank you for reading, we hope this covers the question about your trailer brakes locking up. If you have more doubts, reach out to us in the comments section.

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Sean Mendez

Hi, I am Sean, a self-confessed petrolhead. I live in Boise, Idaho with a busy family of four and our energetic Labrador retriever. Thank you for visiting my website. You can find my email on the contact page.

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