First off, I'm not an electrical guru, but am far more of a "paint by numbers" kind of guy. I had to re-wire all of the trailer side of the 7- pin plug a few years ago. Everything worked with the exception of the reverse lights, which I wasn't concerned about. Check that - everything worked until I turned on the vehicle headlights and then tested everything again. Running lights and turn signals are fine , but when I press the brakes the reverse lights come on too. I'm trying to figure out in my head where I went wrong, but considering my non-guru status, am coming up dry. Short of testing continuity of each individual wire with a super long length of wire from the trailer plug to each light, do any of you have an idea? I virtually NEVER tow at night which is why I hadn't tested everything again with the running lights on.