Hi welcome to the hobby, get ready to spend the most $ you ever had. Anyway, first take the tail lens apart and take out the bulb, it should be a 1157 two point bulb. go to the yard sales and swat meets and find a electric adapter that puts out 13.5 v. then sut the ends off and attach a black and red alligator clips, now you have a handy bench tester. plug it in and touch the red clip to one of the bottom nipples and the black clip to the side of the buob. test both nipples. if the bulb works, then get a spray wd40 and clean out the socket, stick a folded sandpaper down the socket and rub the sides. look at the end of the wire nipples, are they shinney or rusted out. you can go to the napa , kragen, autozone and buy just one or two wires that have the nipple ends. while you are there get one of those 12 volt testers, its a ice pick looking thing that has a clear handle and a bulb in it. attach the end of the tester, alligator tip to metal, and stick the ice-pick into one of the wires, turn on the lights, one wire should turn onthe handle, that means that the other in the stop light. have a buddy go to the cab and press the brakes, then stick the other wire with the tester, if the tester lights up then you know that everything in ok up front. if it doesn't then the problem is up front. follow the wire under the truck until it gets to the brake switch. get your tester and ice pick the terminals there are two on the swith. depress the brake and the tester should turn on. if not then the switch is no good or not aligned with the brake stem. make it fun, turn on music, or tv, drink cokes, and go on this treasure hunt. You will get great satisfaction when you find the problem yourself. I am not a mechanic but love to get in there and get full of grease and sometimes figure things out and brag about it for weeks, later,
