Unkown wire and fuel/temp gauge test

[my5thmopar]

1970 D200. What is this wire just hanging out of the harness going to the gauges? Everything is working and I cant find anything unplugged so, I don't know. I also worked on the fuel and temp gauge. Both work but, don't seem accurate. I grounded the sender wire and the fuel gauge goes to the full mark. Does that mean the gauge is working and maybe I have a sender issue. I guess the temp could be a bad sender too because the truck runs on the cool side. I did have the radiator re-cored with larger tubes. Suggestions? Craig