Troubleshooting The T-Connector Vehicle Wiring Harness For Ford Transit T350

Question:

I purchased a kit for my 2016 Ford Transit 350. I installed it last week but am having trouble. When my headlights are on, the lights on the trailer come on. But they do not light up for turn signals or braking. Any ideas what might be wrong? Tried the trailer on another vehicle and the lights work fine on it. The lights on my vehicle still work fine.

asked by: Jason H

Expert Reply:

Not to worry, this is a common issue and I will be happy to help you get this issue working. Since you have connected the trailer to another vehicle and the lights work on it, you have isolated the issue to your tow vehicle, which eliminates half of the troubleshooting process.

The first step I would take is to use a circuit tester like part # PTW2993, to test the pins on the connector for proper function. I've attached a video that shows how to test a 4-way trailer connector for proper function.

If the trailer connector tests okay, then there could be a ground issue on the trailer that isn't affecting the other vehicle that you tested the trailer with, which can happen. If this is the case, I recommend checking all of the ground connections on the trailer for corrosion or a loose connection.

If the connector on your Transit 350 is not operating properly, Since the brake and turn signals are not working when the running lights are on, this maybe a ground issue. The grounds on the harness may be weak because when you try to use multiple functions like running lights and turn signals or brakes lights, the connection isn't strong enough to handle the amount of power needed. I recommend is rechecking the ground to ensure they are attached to a solid conductor and have a corrosion free connection.

I have a complete install video attached if you need to retrace your steps.

If you still have issues feel free to can contact me for more help.

expert reply by: Timothy G