How Do You Wire a Fuel Gauge? | Reference Wire a fuel gauge by first disconnecting the old dysfunctional unit to replace it with a new one. Obtain 12-volt power from the fuse box using a standard wire, and connect it to the positive terminal of the fuel gauge. Troubleshooting And Replacing Your Ford Fuel Gauge Auto wire; Butt connectors; IMPORTANT - Things you need to know before you start: The fuel gauge is a fairly simple electronic. The fuel gage circuit consists of the sending unit in the fuel tank, the gauge in the dash, and the wiring and dash wiring (or circuit board) between them.