On the way home last Wednesday evening, I stepped on the brakes and had the entire electrical system short out for a second. This happened 3-4 times and then stopped. This only occurred with the headlights on. Upon arriving home, I found that I do not have rear side marker lights or rear tail lights or license plate light, but the front side marker lights are lit. Brake lights work fine, backup lights work fine, turn signals work fine. I took apart the tail lights, checked for shorts and found a loose ground on the passenger side, fixed it, no change.... I have managed to fix the Key in column buzzer and the horn, but still no tail lights. I replaced the headlight switch.... no change ( Note: The Autozone switch is WRONG!!! The O'Reiley switch is the correct one!!!) I do need some color code help. My manual doesn't give wire colors. What color wire is the power for the rear sidemarkers on a 1979 Ranchero??? Also, I found a blown fuse in the lower right hand corner of the fuse block, the writing is worn enough not to be able to read it. It had a 30 Amp fuse in it. If I replace the fuse I get the shorting out with headlights on and stepping on the brake. With it removed, the car runs fine and all the lights and accessories still work.... Weird huh? So what is the fuse for, again my supposed repair manuals do not show a fuse block layout.... Thanks for any help you can offer, I just need to find the open wire!!!