Whats wrong when your brakes lock up on the front axle?  It had a grounding problem and my sons in law worked on it.  They thought they had fixed it, when I hooked to it this morning the brakes dragged.  When I unpluged it they were free.  My brake controler in the truck didn't light up either.  Can anybody help?

You are getting a constant 12v source to your brake circuit. Take a multimeter and see if the truck's blue wire is hot all the time. When the brake pedal is not activated, you should only have one hot wire which is the truck's B+. This furnishes power to your interior lights.

If you only have one hot wire in the truck's receptacle, then, as Robdnorm stated, check the trailer's plug. Pull the shell off exposing the terminals and check each wire for frayed or broken wiring ends. The blue wire normally goes to the brakes. It should not be powered unless the truck's controller is activated by the brake pedal.

If you have brakes on both axles, one of your circuits has a open, and is not allowing current to the rear axle. One blue wire goes from the plug to an area near your front axle. There it splits to both sides. In addition, a splice feeds another wire to the rear axle where it again splits, and feeds both sides. Most brake installations are seperately grounded through the frame.