Mine never reads full. It is a 20 gal. aftermarket tank located in the rear and I have never been able to put more than 15 gals in when reading empty. Sorry no help here. I think the sender is not installed correctly.
Ron, The Computer Greek I love therefore I am. 1954 3100 Chevy truck In the Gallery 2017 Buick Encore See more pix 1960 MGA Roadster Sold 7/18/2017