Simple.
It's a '91 accord.
I strognly believee is the mechanismm at the back of your fuel gauge that is faulty.
Try taking it out yourselflf and check the mechanismim.
All it might need is just some greasing.
Simple.
No worries, it's a relatively small issue.
Judging by your question i would surely say that the fault lies in your alternator.
It's a '96 meaning to say that the alternator has either been changed once or not at all.
1. Get your alternator check or replaced if necessary.
2. If cost...