Gas gauge voltage

[VetteVet]

Originally Posted by woody82

Okay so if I am getting a reading of 5 volts at that terminal then I better unhook it and leave it until I figure out where the voltage is coming from?
I must have a bare wire touching body somewhere?

You're getting a voltage reading because the 12 volts going to the fuel gauge is going through a resistor on the back of the gauge before it goes to the fuse panel. It's still positive voltage but the reading is reduced by the resistor on the gauge. When you ground the fuel terminal, the circuit from positive to negative is completed and the gauge will read empty.

Running the wire from the fuse panel to the sending unit adds in the variable resistance in the sending unit which varies from 0 to 90 ohms and the gauge should reflect this, depending on where the float arm is in the tank.

In your original post you said you put voltage on the terminal in the fuse panel.
That's the reason I said don't do that. You are bypassing the fuel gauge resistor and sending 12 volts into the fuel tank. This could overheat the variable resistor in the tank and ignite the fuel.

here is a diagram of the fuel gauge wiring circuit.



Notice how the current goes from the battery positive to the fuel gauge and through the resistor and then back to the fuse panel and then on to the sending unit. It doesn't show the fuse panel but after the wire leaves the fuel gauge it goes back to the fuse panel. Then from there it goes to the sending unit in the tank. If this wire does not connect to ground the gauge will show over full.