How do you hook up a fuel gauge?

You will use the oil pressure switch only if you have a diesel engine.

The pressure switch applies power to one side of the gauge only when the engine has started and oil pressure closes the switch. This prevents the gauge circuit from discharging the battery when the engine is not running.

If you have a gasoline engine, the gauge is powered from the ignition switch.

Dean

If your tractor has an external voltage regulator there should be a wire from the "L" terminal on the voltage regulator to a terminal on the pressure switch. Then there should be a wire from the other terminal on the pressure switch to the + terminal on the fuel gauge and to the light switch. The pressure switch is usually plumbed in behind the oil pressure gauge. The pressure switch is intended to keep the battery from draining through the gauge or other accessories when the engine is off. There should also be a fuse in the circuit. The gauge works on a resistance of 33 to 240 ohms from the tank sender unit. If you have power to the gauge with the engine running and it's still not working you can check the gauge by momentarily grounding the terminal on the sender unit on the top of the tank. The gauge should go to full scale. If it does,you have a bad sender unit. If it doesn't,you have a bad gauge or broken sender wire.
I hope this helps.

Don