Troubleshooting Trailer Brake System That Activates Once Trailer Is Plugged in to Vehicle

Updated 11/10/2021 | Published 11/06/2021

Question:

I recently installed a Tekonsha 80500-POD brake controller and the T-Connector for a 7 Way blade on my 2019 Nissan Frontier. When everything was hooked up I tested the system using the Tekonsha 6562 Seven Way Tester and Emulator. The light on the brake controller was green to red with the emulator installed and slide activated. Which, as far as I understand indicates that every thing was functioning correctly. When I hooked the 7 way from the trailer to the 7 way on my vehicle the light on the controller was off and the trailer brakes were locked up. Can you tell me what happened?

asked by: LEE L

Expert Reply:

Since the # 6562 emulator shows that the vehicle side of the equation seems to be working okay, I don't believe the brake controller is your issue.

From what you mention, it sounds as if the trailer itself might be wired incorrectly. If the connector on the trailer has the brake output circuit and the 12v feed reversed, it would explain why the brake controller isn't 'reading' the trailer correctly and why the trailer brakes instantly lock up once the trailer is plugged in.

I'll link to a help article that includes trailer wiring diagrams, and I'll also provide a photo showing how the plug on your trailer is supposed to be wired.

expert reply by: Mike L