Like the brakes on your car or truck, trailer brakes can lock up, engaging harder than they should and generating more friction than the tire traction can handle. Abrupt brake lock-ups can cause skidding and loss of control, potentially leading to road accidents. If your trailer brakes lock up, they might have a problem that you should immediately look into.
Here’s Why Trailer Brakes Are Locked Up
What might lock the trailer brakes in place? Here are some of the most common reasons for trailer brake lock-ups on the most common type of trailer brakes:
Malfunctioning Power Regulator
The power regulator manages the current flow, ensuring the proper voltage reaches the brakes when it should.
If the power regulator develops a problem, it might allow the current to reach the trailer brakes with a higher-than-normal voltage. The higher voltage makes the brakes engage harder than they should, potentially leading to a brake lock-up.
Test the power regulator for any issues. If you confirm a problem with the regulator, replace it with a new one.
Incorrect or Shorted Wiring
Wiring issues are another possible problem that causes trailer brake lock-ups. An electric current flows from your vehicle’s wiring harness to the trailer’s harness, supplying power to parts like the electric brakes. If the two wiring harnesses aren’t compatible, the wrong current voltage can go to the trailer, potentially engaging the brakes harder than they should.
You can resolve the issue of incorrect wiring by adding a trailer wire connector. Also called an adaptor, it helps keep the voltage under control as the current travels to the trailer.
Can’t find the right adaptor? You might have to modify your truck’s wiring harness to improve the connection between your vehicle and the trailer, especially if you often tow loads.
Shorted wiring can also cause problems. Excessively high voltage can melt the wire, cutting the connection. You can fix it by finding the damaged section and replacing it with new wiring.
Brake Controller Needs Adjustment
The trailer brake controller is a device that lets you adjust how hard the brakes engage. You can turn up the brake force for more forceful braking or turn it down.
The brake controller might have gotten turned up by accident. Fortunately, you can fix this by dialing the braking force of the trailer’s electric brakes down.
Start by engaging your vehicle’s brakes. Next, move the gain on the trailer brake controller to zero. After resetting the trailer brakes, adjust the gain on the brake controller to the correct level.
Make a habit of adjusting the trailer brake controller every time you hook the trailer up to your vehicle. If you replace the brakes, zero the brake controller and readjust it to match the performance of the new brakes.
Pigtail Wired For the Reverse Signal Solenoid
Many trailers have a flat 5-pin connector or a 7-pin trailer light plug. These parts play a pivotal role in operating the trailer brakes when you drive in reverse with a trailer hooked up to your vehicle.
In a flat 5-pin connector, the last pin is for the tow vehicle’s reverse lead. Its wire connects to the reverse solenoid in the trailer’s tongue. The solenoid prevents you from reversing with a trailer hitched to your vehicle. If you try to drive in reverse, the reverse solenoid activates the trailer brakes.
When you shift your truck in reverse, power flows into the 5th pin, through its respective wire, and into the reverse solenoid. The current electronically disables the reverse solenoid. Now, you can drive in reverse.
The 7-pin trailer light plug works like the flat 5-pin connector. Backing up applies pressure on the trailer’s tongue. If your trailer lacks a light plug, its hydraulic surge brakes engage, stopping your vehicle from reversing.
If there’s a 7-pin trailer light plug, putting your vehicle in reverse sends a current through the backup light wire. The current turns on a solenoid in the trailer braking system, returning the brake fluid to the reservoir. Without the pressurized fluid, the trailer brakes won’t engage.
A faulty flat 5-pin connector or 7-pin trailer light plug might engage the trailer surge brakes when you reverse, leading to the brakes locking up. You’ll need to replace the faulty part.
Lock-Out Key Dropped Out
Instead of an electronic method, you can use a lock-out key to deactivate the trailer brakes. Also called a D-key, the lock-out key stops the surge mechanism from pushing into the tongue, preventing the brakes from engaging and allowing you to drive in reverse.
Some drivers use a nickel instead of a lock-out key. Speaking of which, the lock-out key can fall out of the trailer tongue. Whenever the tongue releases pressure off its sides, the key might get dislodged. This might happen when you drive your tow vehicle forward.
If the lock-out key falls out, the trailer brakes can engage when you drive in reverse. This can lead to trailer brake lock-up. If you repeatedly shift from forward to reverse multiple times during trailering work, the lock-out key can drop out of its slot.
Switching to a magnetic key can prevent the loss of the lock-out key. The magnetic key sticks to its slot, minimizing the risk of it dropping out of the trailer tongue.
Alternatively, you can tape the lock-out key to the slot’s back. Since adhesive tape wears out, you must regularly apply new tape to keep the key attached to the trailer tongue. If you use a nickel, you should definitely tape the coin to prevent it from falling out.
Brake Issues
Last but not least, the trailer brakes might have an issue. Check the brakes for problems. Faulty parts might make the brakes engage harder than they should.
Trailer brakes help keep you safe when you drive with a trailer hitched up to your truck. If the trailer brakes lock up, find out what went wrong and take steps to fix it.
Types of Trailer Brakes
There are four different types of trailer brakes commonly used on light vehicles:
- Electric brakes are the most common, working through an electrical connection with the towing vehicle with a brake controller to manage the force and timing of the trailer’s brakes. The controller adjusts the voltage sent to the electromagnets in the trailer’s brakes, which are drawn to the hub surface of the drum, using a lever to press the brake pads against the drum, stopping the trailer.
- Surge brakes activate when the towing vehicle decelerates. The trailer pushes against the hitch-mounted spring to compress a hydraulic “master cylinder” that applies the brakes as the vehicle is stopping. This is commonly used on U-Haul trailers.
- Electric Over Hydraulic – An electric signal from the towing vehicle activates a hydraulic pump that applies the hydraulic brakes on the trailer.
- “Overrun” Brakes work by the trailer “running into” the towing vehicle when it slows down, activating the brakes mechanically. This is vaguely similar to the surge brakes.
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