I have a 15 gallon Harwood fuel cell in my 68SS. The fuel level gauge always reads half a tank (much to my dismay one evening), doesn't matter if it is empty (refer to previous note) or full. I have checked the wiring and it all looks good. The gauge is somewhat new. I disconnected the positive lead to the cell and the gauge jumped to a full tank, so I'm hoping the gauge is ok. I am running out of options, so I'm hoping it is the sending unit. My question is: how many ohms will the unit read with an empty tank and then a full tank? The tank has foam in it, so is it possible the foam shifted and has the unit stuck some how? I have never seen a sending unit, so I'm not sure how it works. thanks for any help...