brake/tail light wiring

[nevets1215]

I am new to this and this is my first message and i need a little help. I have a 68 chevy c10 and the tail lights, brake lights, and pretty much all the lights at the back of the truck arent working. My problem is when i actually plug the harness from the switch to the wire harness going to the lights at the back. if they aren't plugged they work, took a test light to them, but once i plug it in the wires get super hot and actually start smoking, can anyone give me any advice on this i've looked for broken wires and cant find any. Any help is greatly appreciated.
Thank you