trailer wiring is about as simple as it gets. a hot to each light and a ground. a kid could wire one.i don't understand. for 30.00 you can put a complete kit on most any trailer.they even come color coded so you can't screw it up.
You're right in that 12V wiring is as simple as wiring gets. The problem isn't with new stuff. The problem is gremlins in older stuff, especially stuff that doesn't have any loom around wires strung inside of small spaces, like a trailer frame. Is your grounding problem the ground wire, the connector, or has your wire worn through due to no loom and you're grounding inside of the trailer frame? Or a combination or all 3? Regarding brakes, the above grounding scenarios could be the issue, or your actuators could be faulty, or they could be rusted open, or shut. If you bought used, add in that lord only knows what sort of madness resided within the cranium of the trailer's previous owner.
