Trailer Brakes Only Activate When I Hit Manual Override On the Brake Controller

Updated 01/06/2020 | Published 01/04/2020

Question:

We recently completely rewired our trailer. Lights, Brakes, emergency break away, new plug. So its all brand new wiring on the trailer. All the lights work like they should. All brakes work through the brake controller only and not with the trucks brake pedal. We have tried 2 different trucks and the same thing happens, and only with this trailer. it doesnt do it with the other trailers that we pull. What do we need to do to fix it?

asked by: Benjamin J

Expert Reply:

It sounds like you have pin pointed the issue is on the trailer because it only brakes with the manual override of two different brake controllers in two different trucks. Since the issue is on the trailer the culprit most likely is related to a bad or weak ground on the brake assemblies. I recommend to take a look at the grounds of the brake assemblies to make sure they are attached to a clean bare metal surface of the trailer frame or they are all properly connected the main ground of the trailer. A poor ground can cause a voltage drop on the brake output wire. When you hit the manual override it sends back the max voltage available to stop the trailer in a hurry. While using the brake pedal especially when the vehicle is in park it does not send back as much power which is why the brakes aren't activating.

If the grounds are okay, you want to make sure the brake output wire on the trailer is 10 or 12 gauge to start. Any gauge smaller than 10 or 12 can cause a voltage drop as well. You also want to take a look at the blue wire to make sure there is not any damage or exposed wiring. I also recommend to take a look at the connector on the trailer itself. If the connector is rusted it may not get a good enough connection with the vehicle's plug.

Please let me know if this doesn't solve your issue and I can troubleshoot with you further.

expert reply by: Heather A