Brake Controller Shows Trailer Connected with No Trailer Connected

Updated 08/24/2018 | Published 08/23/2018

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Question:

Hello. I asked this question yesterday: I just installed the curt Adapter 4 Pole to 7 Pole and 4 Pole w/Test Lamp as well as a Tekonsha Prodigy P2 Trailer Brake Controller - 1 to 4 Axles - Proportional # 90885. I installed the items exactly as instructed. The brake controller led screen is saying the trailer is hooked up. .C. Any advice? I got a response and I appreciate that. I was told to unhook the led light to see if the controller is being tricked into thinking the power the light on the 7 way is drawing is the trailer hooked up. I unhooked the 12v wire from the 7 way to the battery. The brake controller was still on. I assumed unhooking that wire from the battery would turn off the controller. After unhooking the 12v wire from the battery the led screen still reads .C. Now the led light on the 7way labeled BK is flickering.

asked by: Ian

Expert Reply:

There is definitely a short somewhere and since you disconnected the 12 volt power wire from the newly installed 7-Way the only items left that could cause this is the brake controller and its wiring. But make double sure that the white ground wire on that adapter is attached to a clean bare metal surface. Not that a short to ground or weak ground would cause this exact issue but better safe than sorry.

On the 4- to 7-Way adapter the blue wire is the brake output wire for the trailer brakes. If that wire at any point got pinched or there is exposed wiring touching a metal surface then it could cause this issue.

Another possibility is that inside the adapter there is some other wire touching the brake output contacts inside the back of the 7-Way. You might be able to open it up to look. There are some ways you can test the brake controller as well to determine if it is the problem.

In the truck cab you will need to sever the blue wire several inches from the back of the controller. Then use a circuit tester such as # PTW2993 to test the end of the blue wire coming out of the controller. It should only have power when you apply the manual override. If it shows power at idle, then there is something wrong with the controller and it will need to be replaced.

If it tests fine, then reconnect the blue wire. You can test the brake output pin and it should only show power with the manual override. If it shows power any other time, then there is a short somewhere between the connector and the brake controller you will need to track down as mentioned before.

I have included some additional links on testing and troubleshooting brake controllers for you.

expert reply by: Michael H