Here is the simple idea behind gas gauges,
1- voltage is feed to one side of the gauge from the ignition switch, 6v if stock, 12v with reducer to 6v if altered.
2- from the second post on the gauge, a wire or series of wires, run to the sending unit in the tank.
3- the sender in the tank has a variable resister built in it that changes resistance depending on the fuel level, 0 to 30 ohm
4- the fuel sender is grounded to the tank. The tank should be grounded to the frame.
5- the sender varies the amount of ground circuit going to the gauge, so unhook it and the gauge reads empty, ground the wire and gauge reads full.
You could have a bad ground wire at the tank, bad sender in the tank, bad gauge, poor connection at the gauge, bad fuse.
Let us know what it is or is not doing and someone here should be able to fix it. Joe
