Fuel Gauge Help!

2 gauges, both over 40 yrs old, do the same thing, no surprise. I've been inside over 100 of these SW gauges.
Inside the gauge is a bi-metal strip that bows when heated. That bow action moves the needle. The heat comes from a electrical current passing through ni-chrome wire wound around the bi-metal.
That wire is/was insulated with a silk-fiberglass blend that was originally a pale yellowish color and very fine/thin.
I often find a bow in the bi-metal at room temperature meaning its temper is weakened.
I often find the winding coated with a black crunchy collection of crap that makes it look 5 times its original size. I think the very worst examples were in a smokers car. Anyway...
All of these age related faults effect the needle motion. Nothing lasts forever