I'm trying to cobble together a working gas gauge system for my '29. I've got a '30 tank in it with a sending unit. I've got an original '30 gas gauge, and a brand new one. I'm pretty sure the '30 gauge is not good--it reads empty all the time, only moving when I tap it. The new gauge reads full--even when the tank has 3 gallons of gas in it. Ths is how I've got it wired: one wire from sending unit to "sending unit" terminal on gauge and one wire from the "coil gauge" spot on the ignition switch to the other terminal on the gauge. Do I need to have the sending unit grounded at the tank? If I disconnect the gauge from the sending unit and ground that terminal, the gauge reads full. Thanks, Dave