I just bought my truck and hauled a trailer for the first time this week. The truck does not have a brake controller but does have a 7 pin rv hook up. I have a dump trailer that takes a 6 pin, so i put the 7 to 6 pin adapter on. I went to haul the trailer and when it was plugged in 1 wheel was locked up, i unplugged the lights and it rolled fine. Is it grounding out and causing the brake to set?? Later i plugged it back in and it rolled fine, and intermintently would lock up. Any ideas?? Thanks Roger.