Fuel gauge 2005 softail repair

Sounds like a loose or corroded wire connection or a broken and intermittent defect for power OR ground but see below for generla diagnostics and etc:





When the ignition switch is ON the fuel gauge is connected to 12 VDC, current flows through the gauge and the variable resistor in the fuel gauge sending unit to ground. The sending unit float controls the amount of resistance in the variable resistor. Malfunctioning fuel gauges may be the result of a fuel gauge sender or a fuel gauge not being properly grounded OR there may be a defect in the fuel gauge sender or in the fuel gauge itself OR there may be an open circuit caused by a loose or disconnected connection or a broken wire between the ignition switch to the fuel gauge.



A suspect fuel gauge system can be tested by FIRST removing the gauge and grounding the Y/W wire of the fuel gauge sender located at the bottom of the gauge, turning the ignition switch ON at which point the fuel gauge must indicate FULL. And if it does so then the fuel gauge is functioning correctly.And if it does not read FULL then get a multimeter set to the RX1 scale and measure the resistance of the sending unit by placing one of the meter probes on the Y/W wire and the other probe on a good ground. THEN for Softail if the fuel tank is full, the reading should be 27-40 ohms. an empty tank should have a 240-264 ohm resistance and a half full tank will be approximately 97-118 ohms. FOR ALL MODELS if there is a very high meter resistance or infinity reading the sender may be "open" or not grounded. In this case check to see if the sender and fuel tank are grounded by placing one of the ohmmeter probes on the flange of the sender and the other probe on crankcase and if the ground is good the meter must indicate one ohm or less and if the reading is one ohm or less the sender is defective and requires replacement and if a higher resistance reading is obtained you will need to check for a poor ground wire. THEN you can check the voltage to the O/W (+) wire and the BK (-) wire of the fuel gauge connector if the gauge did not indicate FULL and the correct reading will depend on the source voltage and the level of fuel in the tank or the position of the sender float arm on the variable resistor etc. If there is NO battery voltage present there may be a broken, highly corroded or disconnected power wire. If you cannot find a problem using the above testing replace the gauge itself.