this is for my 1961 109 . it has the generator still, and has a negative ground system.when the switch is turned on, the gauge always goes to full. i pulled the wire off the sending unit and it still goes to full (pegged) no matter how full the tank is.i even switched the two wires on the back of the gauge and it still goes to full. this is the only electrical problem on the whole truck and i'd like to have it repaired , thanks!