Troubleshooting EOH Actuator That Will Not Release Brakes

Question:

My electric over hydraulic brakes will not release what could cause the problem

asked by: Eric

Expert Reply:

If your EOH brakes will not disengage the problem could either be mechanical, as in a malfunction with the master cylinder, a clog in the hydraulic lines or broken parts in the brake assemblies themselves. Or it could be electrical in origin, meaning that electrical power is reaching the actuator when it should not.

Troubleshooting this type of problem is easiest if you disconnect the trailer and test the tow vehicle and trailer separately.

If the brakes release when you unplug the trailer then this suggests that the problem is on the vehicle side. This issue could be a bad brake controller or a short in the vehicle's wiring that is allowing 12V power from another circuit to leak into the brake circuit. A badly corroded connector could cause this and so could damaged wire. Check the socket on the vehicle and the wiring upstream of it for any signs of corrosion on the contacts or damage to the actual wiring.

If the brakes remain engaged even when the trailer is disconnected then this issue could be caused by power from the breakaway battery or the auxiliary battery reaching the brake circuit. If you can, disconnect all trailer-mounted batteries to remove any chance for power to reach the actuator. If the brakes remain engaged in this circumstance then this suggests a mechanical problem on the trailer.

If you have a circuit tester like # PTW2992 you can test the vehicle socket. Ground the tester and apply it to the contact for the brake circuit, shown in the linked photo. If you detect brake signal here without activating the controller then the controller is likely to be damaged.

Please try these tests and if they do not reveal the cause for the problem please tell me and we can try additional steps.

expert reply by: Adam R