The Stovebolt Site Forums The Shop Area The Electrical Bay Gas guage question 64 C10

Better for you to do the search, as Martin suggested. I've learned many things about issues other than what I was searching for while doing so; and found solutions to my issue.
But to give you a head start, you have two posts on the back of your gauge, One is 12v with the key on and the other goes to the sending unit on your fuel tank. As your float on your sending unit goes up and down, it increases/decreases the resistance-----which causes the needle on your gauge to move.
Read through the threads will help you diagnose your problem. It could be a number of things: your float is full of fuel, your fuel tank is not grounded, your fuel sending unit needs to be replaced, etc.
Do your search, learn many things that will help you in the future to keep your C10 on the road, and if you run into a problem, let us know. Good luck!