I bought a new to me tow rig for my 29 fountain it is a 2011 F250 Super Duty. When attempting to back to trailer into my storage facility for the first time with the new truck the surge brakes locked up on me. I have never had an issues with this on my 2013 Silverado, so I dont believe it has to do with the trailer. Looking this up online, it could be a fuse, or some potential wiring that needs to take place to ensure reverse light power gets to the trailer in order to lockout the brakes from engaging. My trailer is a brand new National, but they provided me a cheap adapter that goes from my trucks 7 pin to a 5 pin. I plan to start by replacing that, but wanted to see if anyone here has had this issue in the past with their Ford F250 and has an easy fix before I break out the multimeter and start diagnosing.

Does your trailer have a reversing solenoid?
Have you verified that the reverse light pin on your 7-way is providing 12V+ when the truck is in reverse?
Check your manual for fuses and trailer plug instructions for enabling beyond the 7 way. There is often an additional fuse that needs to be installed.

There is a relay needed in the underhood electrical distribution box. I needed to put one in my 2002 but my memory is not what it used to be. Sorry.

Pic posted for sonics42

Thanks everyone. Found the issue was with the 7 pin to 5 pin connector. It was just a coincidence that it broke between towing the boat with the different trucks.. Bought a "better" one, and have had no issues since.

Thanks,