I have a 1939 Cadillac LaSalle frame off restoration. The dash is original and all gauges work well. But the needle in the gas gauge gyrates wildly when driving. The needle bounces between E and F and then settles about where it should and begins gyrating again. Only when the gas tank is full does the needle remain steadily at F. Is this a float problem in the gas tank, a ground issue or what.
Any ideas or suggestions are appreciated.