Same thing happened to me with the Runtz resitor it heated and shorted out to the back of the gauge. I am using the original sending unit (1950 truck) but I gounded the tank to the cab like the 52-and later trucks (wire from one of the sender screws to cab brace). I could never get it to work until I bought a new 12-volt gauge from Classic Parts works like a champ now. I also was really careful when I installed it to use new cardboard seperators like the original on the back of the gauge. They are available from www.classicchevroletparts.com but I couldn't find the item number this morning.