Troubleshooting Trailer Brakes That Won't Release

Updated 09/25/2017 | Published 09/23/2017

Products Featured in This Question

Dielectric Grease for Electrical Connectors, 2 oz.

(1491)

$10.94

Question:

I plug in or not electric brake wont release. Light is not coming on on controller. Brakes wont release.

asked by: Mickrell M

Expert Reply:

If your trailer's brakes remain engaged when it is plugged in to your vehicle, even when the controller does not indicate that it is generating a brake signal, this most often means that there is a short in the vehicle's or trailer's connector.

What can happen is that corrosion (or water or trapped foreign material) inside either the vehicle socket or the trailer plug can cause two different circuits to become bridged together. This could, for example, allow the power for trailer lights to bleed over to the brake circuit, causing it to engage the brakes when they should not.

The best fix to this issue is usually a new trailer connector, such as # 37185 or # H20046, but sometimes the corrosion (if that is indeed the cause) can be dissolved with a spray-on electrical contact cleaner such as Caig De-Oxit. Clean properly-functioning connections can be protected with an application of dielectric grease like # 11755 which blocks entry of moisture.

Another potential cause is incorrect installation of the controller red wire. This wire carries the signal that triggers the controller to generate a brake power signal for the trailer. If this wire is connected to the wrong circuit on the vehicle it could cause the brakes to engage when they should not. This read wire should connect to the cold side the brake light switch, which is the wire that carries a signal ONLY when you press the brake pedal and at no other time.

expert reply by: Adam R