Does your trailer feel like it’s pushing you every time you brake? Or do the trailer wheels lock up suddenly when you slow down? These could be signs that your trailer brake controller isn’t working as it should.
Your brake controller is responsible for applying braking force to your trailer when you press the brake pedal. If it’s not set up or functioning correctly, stopping distances increase, and towing can quickly become unsafe.
Luckily, there are a few simple checks you can do to identify common trailer brake controller problems — and many of them can be done at home.
Follow these steps to get started.
Steps to Identify Trailer Brake Controller Problems
Visual Inspection
Start inside the vehicle and check the brake controller itself.
Make sure the controller is:
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Securely mounted
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Positioned at the correct angle
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Not loose or moving while driving
Next, inspect the wiring:
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Look for loose or damaged connections
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Check the trailer plug and socket for corrosion or dirt
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Inspect the trailer wiring for wear or damage
Any visible issues here can affect how the controller sends power to the trailer brakes.
Power and Display Check
Most modern brake controllers have a display or indicator light.
With the vehicle on:
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Confirm the controller powers up
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Check that it detects the trailer when plugged in
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Look for error codes or warning messages
If the controller doesn’t power on or fails to recognise the trailer, there may be a power supply, earth, or wiring issue.
Manual Override Test
The manual override allows you to apply the trailer brakes without pressing the vehicle brake pedal.
At low speed:
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Activate the manual override
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The trailer should slow the vehicle smoothly
If nothing happens, the controller may not be sending power to the trailer brakes. If the brakes grab suddenly, the gain may be set too high.
Gain Adjustment Test
Incorrect gain settings are one of the most common brake controller problems.
With the trailer connected:
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Start with a low gain setting
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Gradually increase it while testing at low speed
The correct setting allows the trailer to brake evenly with the vehicle — without pushing or locking up.
Wiring and Earth Check
Poor wiring or earthing can cause weak, delayed, or inconsistent braking.
Check:
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Earth points on both vehicle and trailer
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Wire size between controller and trailer brakes
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Condition of plugs and connectors
High resistance from poor connections can reduce braking performance significantly.
Check Trailer Brake Components
If the controller appears to be working, the issue may be in the trailer itself.
Inspect:
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Brake magnets
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Brake shoes and drums
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Trailer bearings
Worn or damaged trailer brake components can cause poor braking even with a correctly functioning controller.
Check Warning Lights and Fault Codes
Some brake controllers display fault codes or warning indicators when a problem is detected.
If a warning light stays on or appears while driving, refer to the controller’s manual for guidance. Persistent warnings often indicate wiring faults or brake circuit issues.
Final Note
Paying attention to early warning signs like poor stopping, jerky braking, or trailer push can help you catch brake controller issues before they become dangerous.
If your basic checks don’t resolve the problem, having your towing setup inspected by a qualified technician is the safest option. A properly functioning brake controller is essential for safe and confident towing.
Need advice? Get in touch with our team to learn more about setting up and maintaining a reliable trailer brake controller system.
