Fuel Gauge Sending Units compared

If you use resistors to do some testing, make sure they are high enough wattage. At full scale, 12 volts divided by 13 + 10 ohms (gauge + sender) is about 0.5 amps. For the resistor, 0.5 amps times 10 ohms is 5 watts. A little quarter watt resistor will burn your fingers & change value after a bit. No need to ask how I know that.