My gas gauge does not work at all. How do i diagnose the problem, to find out if this needs a new sending unit or if there are other issues?
Disconnect the fuel gauge sending wire from the fuel tank sending unit, with key on the fuel gauge will either go to Full or empty, now ground the fuel sender wire to a good ground, the gauge should do a full sweep to the opposite end of the gauge.
If you get no change on the gauge during this test you either have a bad gauge or a break in the sender wire to the gauge.
Most of the time it is the sender.