I have the unit out of my car so checked it with the VOM-got goofy readings too. Been sitting for decades, and I expect the pot gets corroded and so as one moves it it gets jumpy. One can reduce this to a degree by "polishing" it, moving back and forth repeatedly. The best way to check is a la the shop manual (under gauges and instruments,) by inserting it between instrument voltage and the gas gauge and checking over a full swing. VOM's run on low voltage, and will seem more erratic than the gauge, which operates on 5 or so. A last resort is to take the cover off the pot and clean it up. NOS doesn't count with electrical components that corrode.