Mercedes® Fuel Tank Sending Unit Sensor, 1973-1980 (107)

If your fuel gauge is working erratically, or not working at all, and you are getting power to the sending unit itself, you need to replace the sending unit. Chances are one of the delicate wires inside the unit has broken or the float has broken or stuck. On diesel models, an algae growth can also disable the sending unit, but it is difficult to clean and the sending unit would have to be replaced also.