Well im trying to pull my enclosed trailer with my 2007 GMC 4500. Did it a couple years ago and it worked. Just hooked it up today and the whole left side of the trailer doesn't work! No lights what so ever on that side. Now the right side works (Turn signal, brake, etc..) But nothing on the Left side. So i hooked up the 4500 to the open trailer and i have NOTHING what so ever working on that trailer. In the meantime EVERYTHING works when i hook up a pickup truck to these trailers. Anyone know what the problem sounds like??