Non Rallye fuel gauge either full or empty

I have had 30 cars and damn near everyone I buy needs a sender...so I have some experience with this LOL. All checks out. I just find it odd the gauge will only read full even though the sender works fine.
Guess I will try the gauge tomorrow with a 1.5 volt battery and see if I can get it read half way...I assume if it doesn't the gauge will be the issue?