The pot is adding resistance throughout the range of the rheostat on the sender. The hard part is knowing exactly how much is in tank. Empty it, add a gallon and call that empty. Fill it and call that...well, you know. You can buy a 30 ohm gauge from Autometer and sell the other gauge and sender. But of course, I don't know if this is for a boat, an airplane, a go kart, a TF or an AD or a car. Wrench fetchers should know to state the vehicle. Sometimes that may help those trying help those who ask. In this case maybe doesn't matter, but a good practice to follow. To test this fix don't cut your sender wire, disconnect it from gauge and add pot to it and run a short wire from pot back to gauge. Adjust pot. If it does not work send the bill to Johntsmith.
