Troubleshooting Horse Trailer that Locks Up Trailer Brakes When Connected to Truck

Question:

I have 2006 GMC Sierra 2500HD I recently purchased a Draw Tite controller and Jumper harness # 3015-P to connect to factory plug. The truck has what appears to be a factory GM 7-way plug. When trailer is plugged in controller does not recognize the trailer is connected and trailer brakes are locked up? The Trailer is a 2006 Thuro built horse trailer with 2 axles. We tried to hook the truck up to another trailer and same problem? Thanks for your help

asked by: Ronnie M

Expert Reply:

This is a fairly common problem with horse trailer wiring. The problem is that there are two accepted ways to wire up a 6-way connector and the only difference is that the brake output signal and the 12 volt signal are swapped. Which means that if you have a trailer wired one way and a truck the other way you end up with the brakes locked up all the time.

What you need to do is swap those circuits and it'll work like it should.

I attached a picture of a 6-way for you to check out as well.

expert reply by: Jameson C