How to Troubleshoot a Tractor Fuel Gaugeby Don Bowman
A fuel gauge on a tractor works the same as an automotive fuel gauge. The most important thing to remember is that the gauge and the sending unit must be a matched pair. For example, a Chevy gauge and the sending unit are both operating in the zero- to 90-ohm range. There are several different gauges and sending units so, unless both are being replaced, the operation range must be found for a proper indication.
Turn the ignition switch on. Touch the negative lead on the voltmeter to a good ground and touch each side of the fuses with the positive lead of the voltmeter to check for blown fuses. Replace any fuse that does not show power on both sides of the fuse.
Check for 12 volts to the rear of the fuel gauge on the terminal marked BAT+ by touching the positive lead of the voltmeter to the BAT+ terminal and the negative lead to a good ground. Check for an open (broken) wire between the gauge and fuse if there is no power.
Look for any loose connections on the rear of the gauge. The gauge should have a good ground going from the negative terminal to ground. Put one of the ohmmeter's leads on the negative terminal and the other on a good ground. There should be no resistance. If there is resistance, repair the ground.
Check for power at the sending unit. There should be 12 volts. Check the ground to the frame for resistance with the ohmmeter. If there is power at the sender and a good ground and the gauge still does not work, the sender is bad.