[Capt. Debbie]

Problem can be in three spots. #1 the sending unit is not free swinging and traveling vertical ( as suggested) and the resistor that varies with it is not changing.

#2 a bad connection. It's low voltage and a bad connection can consume some of your signal. That would still track on the guage up and down. But would not go full scale up.

#3 a bad guage. Likely a mechanical failure within the guage itself. That's what the piolts used to tap the guages on old fighter planes for. Mechanical guage is stuck.

The hardest to deal with (in most boats) is the in-tank sending unit. Often inaccessible under the deck with little or worse- no access.


Good luck!