1976 Scamp fuel gauge problems

FYI, the voltage at the instrument panel starts out near battery voltage (approx 14 volts), gets regulated down to approx. 5 volts and splits off to the gas gauge and the temperature gauge. For the gas gauge circuit the current goes through the gauge, down the wire all the way to the tank, through the variable resistor (the sending unit) and finally to ground. If there is an open anywhere in that series circuit you'll get no reading. It should be pretty straightforward to troubleshoot. Good luck.