I have a 2003 ford F-250 and used the the factory hook up for the brake controller and I have a reese contoller. When i am not hooked up to the camper it only has the dot come on when i hit the brakes witch it correct. But when i hook up the camper it still only has the dot when i hit the brakes and the trailer brakes dont work. But if i turn on my headlights they work. and the digital display has a reading on it. My question is why does it only work when my light are on.