How to Troubleshoot Electric Brakes

Electric brakes are used on trailer and work primarily with magnets. There are a number of problems that can occur with these brakes, which mainly include becoming weak, noisy or intermittent; surging, grab locking or dragging; or not working at all. There are several possible causes for these problems, and some can lead to multiple problems. When troubleshooting electric brakes, look for issues that can cause multiple problems, and then check for anything that might cause something specific.

Instructions

Check the brake adjustment and adjust it properly, if needed. This can result in no brakes, weak brakes, dragging brakes or noisy ones.

Look for and replace any weak or broken springs. This can cause noisy, dragging, grabbing or locking brakes.

Replace the brake linings if they are excessively worn or contaminated. Worn linings will cause noisy brakes, while contaminated ones can make them noisy, weak, grabbing or locking.

Make sure the trailer ground is adequate. A ground through the trailer hitch is inadequate and can cause intermittent or surging brakes.

Check the electric circuit and look for a short. This can be a cause of weak or no brakes.

Inspect the brake controller. Dragging brakes occur from a hydraulic defect in the controller or an insufficient gap between its contactor strip and coil. Disconnect and check the controller's red wire if it isn't modulating, which can make the brakes grab or lock. Rewire the controller and check its operation if you have no brakes. Bench-test the controller and replace it if needed.

See if the brake magnets are worn or defective, and replace them if so. They can cause weak or no brakes.

Check the selective resistor, which is needed when the brakes have more power than is needed for the load carried. No resistor makes the brakes grab or lock, an incorrect resistor setting makes them weak and a defective one leads to no brakes.

Make sure the flanges are properly installed. A bad location can make the brakes drag, grab or lock. Check with the axle manufacturer if the flanges are improperly installed.

Look for a bent backing plate if you have weak or noisy brakes. Repair the plates and their flanges if needed.

Look for an open circuit if you have no brakes. This can include broken wires, loose connections, improper grounding or a bad connector plug between the vehicle and trailer.

Adjust bearings if they aren't properly adjusted and causing noisy brakes. Replace any worn or damaged bearings.

Clean and lubricate the brake assemblies if they are corroded, causing the brakes to drag. Make sure the magnet levers can operate freely.

Turn or replace the brake drums if they are out of round, replace any broken magnet lead wires and adjust any loose wheel bearings. Any of these can cause intermittent or surging brakes.

Look for any loose or dirty connections, make sure you aren't carrying an excessive load or using the trailer brakes only, see that you have brakes on every axle and make sure the wiring is adequate. These can all cause weak brakes.