What can go wrong with backup lights? Mine stopped working last year and I can't seem to figure out what's wrong with them. I replaced the neutral safety switch and both bulbs, but that didn't do anything. One of the sockets was a little corroded, but I cleaned it up and they still don't work. Can anyone explain how they get their power? How do you test them if they only work with the car running and in reverse? Any ideas would be appreciated.