20 Most Recent 2003 Harley Davidson FLSTF Fat boy Questions & Answers

The fuel gauge is really two parts. You have a guage and a sending unit. You must have voltage going to the unit as well. On most models, the wires that supply voltage to the gauge run upwards through a small tube in the tank for the bottom of the tank. There is a connector at the bottom of the tank in most cases.

Using a VOM (volt/ohm meter) unplug the connector beneath the tank and check for voltage with the ignition switch on. You should have approx. 12 volts. Once you've finished this test, turn the switch back to the off position.

Next, you will have to check the sending unit. Remove the gauge from it's rubber gasket that holds it in position on the tank. Carefully work the gauge up and out of the rubber sleeve because the wires are very short. Once you have the gauge out, you'll have to check the resistance of the sending unit with the tank nearly full and then again with the tank nearly empty. If the resistance of the sending unit changes, the problem is probably the gauge itself. If the resistance does not change, the problem is more than likely with the sending unit. Check the sending unit for a good ground as well.

The sending unit is held in the tank by five or six small screws. Remove these screws and lift the unit slightly. Do not attempt to remove the sending unit with the fuel tanks full and the bike on the side stand. Fuel will be all the way to the top of the tank and will spill out when you attempt to remove the sending unit. While lifting the unit, turn it working the float arm out of the tank. Be very careful not to bend the float arm. Once you have the unit out of the tank, you can check the unit's resistance again. When you remove the sending unit, always replace the gasket that goes beneath the unit.

Be very careful, you are working with gasoline and expolsive fumes. Do not smoke or have any open flames near.

Duplicate question already answered

put a multimeter on the coil wire , set the meter to 12 volts dc and turn on the ignition it will be either 12 volts ( 12volt coil ) or 7.5 volts ( 7.5 volts coil) this system is used on may electrical ignitions meaning it starts on 12 volts ( maximum spark with reduced voltage under cranking ) but runs on 7.5 volts ( resistor controlled voltage )