[rotorwrench]

On the King Seeley units, a person can pop the top off and do a good visual for broken wire ends or a cracked carbon resistor. A person can clean the breaker points contacts if they are careful. There isn't a lot else that can be done for them. If it's broken then a person has to look for a good used or NOS unit. There is an outfit that is making a trimmer to use a rheostat type sender but the sender has to fit or be adaptable to the tank bung for it. Some adapters are available but those are mostly for new tanks than the bung doesn't match to original size and screw pattern.

The trimmer units will reset the rheostat to give relative accuracy at full and empty positions by use of trim pots that are adjustable with a very small screw driver. There was a thread about these not long ago on one of the forums but a person may be able to Google fuel interface module or Ohm converter. Speedway and others sell them. I don't now how well they work though.