Took the truck out today to buy a Christmas tree. Drove with the lights on. Got to where I was going and the tail light fuse was blown. Put in new fuse, returned home at sunset. When I started the truck, all the lights flickered until I drove out of the parking lot then the headlights and dash lights worked fine but tail lights were out before I hit the highway. I drove home with the flashers on.. I had after-market turn signals installed and they work without the key. Could this be the problem? Could the brake light switch be the problem? Rear turn signals and brake lights work fine and aren't effected.