R(t), R= resistance, what is t? I use my original fuel gauge with 12volts, It reads full for a long time, then goes to empty fast. The sending unit in the tank has a variable resistor in it, that needs to be changed to make it work right, to adjust the range of the gauge. Putting a resistor in series doesn't quite get it. You can read the resistance of the sending unit with an ohmmeter. with the gauge disconnected, full tank, and empty tank. divide each of those readings into 12(12volts) to get the current range. Somehow I came up with this chart, I think from studying the reducers available in catalogs, it was years ago. Run 6 volt accessories from 12volt system. 1amp load=6ohm 6watt, 1.3amp load=4.5ohm 7.8watt, 2amp load=3ohm 12watt, 4amp load=1.5ohm 24watt, 8amp load=.75ohm 48watt, 12amp load=.5ohm 72watt. Using a dropping resistor is not efficient and they get hot!
