OlBlueit seems to me that I need to know if the gas gauge is in reality a voltmeter or an ammeter.
The gas gauge is what's called a "balancing coil" meter. There are two electromagnets, one with a constant-strength magnet, and another with variable magnetic strength. The position of the needle depends on the strength of the magnet controlled by the tank unit. The resistor is inserted in series with the constant-strength magnet, and the voltage to the sending unit is also reduced by this resistor. Basically, you're limiting the current available to the balancing coil and the sending unit, making both of them operate on 6 volts, not 12.
Jerry
