Troubleshooting Trailer Brakes Lock Up All the Time

Question:

Hi, I ordered a 118266 and finally got a chance to use this with a trailer with brakes. I have a 2012 Nissan Frontier. When i hooked it up, the brakes on the trailer locked up and no lights were on the brake controller. All other functions worked on the 7pin, turn signals, brake and running lights. We hooked the same trailer to my friends truck and trailer brakes worked. I tested the blue wire on the back side of the 7pin and I got constant read of voltage. The brake controller never showed any light at all even when the brakes were being applied. It looks like some one else put this same question in a while back and the answer was that the 12V wire maybe be mixed up with the brake controller wire. I am wondering if this part 118266 has a defect. Any thoughts on a solution. I followed all the videos when installing all the wiring and as stated all other functions work fine. Thanks.

asked by: John D

Helpful Expert Reply:

If there was some type of issue with the part # 118266 it would have been located long ago as this part has been used for a number of years.

Since you tested this on a different vehicle with the same trailer and it worked we can rule out the trailer wiring or brakes on the trailer being an issue but there are still a number of troubleshooting applications I recommend.

Start by testing the brake controller by severing the blue wire a couple inches from the back of your controller. Then use a circuit tester such as # PTW2979 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 an issue with the controller. This is highly unlikely since it is a new controller but you will want to be certain.

If the controller tests fine reconnect the blue wire and move on to the truck side trailer connector. Often, corrosion or dirt may be the cause of a short in a trailer connector. Check the plug to see if there is any type of corrosion built up that may be hampering its functionality.

You said there was constant voltage at the brake output pin on the 7-way but I'm not sure how you tested it because it should only show power with the controller's 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 find.

I have also attached some help articles on testing and troubleshooting brake controllers for you to check out which should be useful.