Symptoms
- Trailer brake controller shows an error or no connection
- Trailer seems to push the tow vehicle when braking
- Brakes feel weak or grabby, or only work on one side
Likely causes
- CommonBrake controller not properly connected or configuredA controller that's unplugged, miswired, or set to the wrong gain won't apply trailer brakes correctly.
- CommonPoor ground connection at the trailer's brake systemElectric brakes rely on a solid ground, and corrosion here can cause weak or absent braking.
- PossibleWorn brake magnets or shoes (electric brakes)Like any brake system, components wear over time and need periodic inspection and replacement.
- PossibleDead or disconnected breakaway batteryThis separate small battery applies the brakes if the trailer detaches, and being dead won't affect normal braking, but is worth checking as part of overall brake system health.
What to do
- Check that the trailer connector plug is fully seated and undamaged, and that the brake controller in the tow vehicle shows a proper connection (many display a readout or test function).
- Test the controller's manual brake activation lever with the trailer connected; you should feel the trailer brakes engage.
- Check the trailer's ground connection for corrosion, similar to a lighting issue, since electric brakes need a solid ground.
- If accessible, inspect the brake magnets and shoes at each wheel for wear, which requires removing the wheel and brake drum.
- Check the breakaway battery charge level and connections, and charge or replace it if needed, even though it's a separate system from everyday braking.
- Adjust the controller's gain setting appropriately for your trailer's weight if braking feels too weak or too aggressive, per the controller's manual.
Tools and parts
- Multimeter
- Basic hand tools
Trailer brake magnets or shoes, if wornSearch: “trailer electric brake magnets or shoe kit for [your trailer axle size]”
When to call a pro
If you're not comfortable inspecting brake magnets and shoes yourself, or the controller shows a persistent fault, have a trailer service shop diagnose and repair the system.
Safety
Use caution
Trailer brakes are a critical safety system, especially for heavier loads; don't tow with known non-functional or severely weak trailer brakes.