Gauge diagnostics

Continuity, yes. There has been hundreds of posts on this board start with a search. In general problems with my cluster......

IVR "socket" fingers were not makking contact with board traces. Had to solder jumpers across. If you have a ralley cluster and the IVR is in the fuel gauge, this does not apply (Your fuel gauge should have 3 terminals if the IVR is inside

Gauge stud nuts corroded. Use "real" nuts and tighten/ loosen/ tighten several times to scrub the contact clean

Bad IVR. Replace with a repop solid state unit.

Bad connections / wiring to the senders. This includes the sender end connectors. Of course the senders themselves

You can power a gauge directly with a 1 1/2V D battery(nothing else connected) and it will go part way up scale