I've seen a post on here that describes testing the entire circuit by manually raising and lowering the float and watching to see it the gauge move correctly. Other than that guess you can check it with an ohm meter to see that the circuit is complete. The first indicator for me is if the needle is in the home position just below the empty mark. Other broken gauges I've had the needle is way off.
Best of luck and I'm sure others will be along with better info!


It's easier to get forgiveness than permission!
1946 1/2-Ton Chevy
1953 Chevy 3/4-ton Factory Stakebed