I've been replacing all of the lenses and lights on a '93 F-150 that a bought a over six months ago, headlights, corners, turn signals, tails ... everything. It was in bad shape and I wanted to be able to drive it at night, safely above all, but also without getting pulled over and harassed. Up front, I even replaced the sockets for all of the bulbs. The turn signals are a 3157 dual filament bulb with a S547 socket. For some stupid reason, the aftermarket socket pigtails have no indication of which wires are which. There are three black wires, how stupid is that? So, I got out my meter and checked them, and then installed the turn signal socket on the right side. I assumed that the other socket would be exactly the same, so I wired it up the same way. Then I've got no left turn signal with the headlights on, and on the dash the left turn signal indicator lit up when I turned on the headlights. Okay, seems like a ground problem. I wired up a new ground connection for the left side, after which the fuse blows. At this point, I know something is very wrong. As it turns out, the order of the wiring coming out of the other socket was completely different, not reversed, but completely random.