I have a 1989 f 250 5.8 the battery light is on replaced the battery the light came on after driving a day later.The battery gauge is leaning towards the minus side.Thank You for any help

 

It means you have a charging system problem.
It could be anything from a loose belt, a poor connection at the alternator, a defective alternator or voltage regulator. Also a poor ground where the regulator is mounted can give the same problem. Don't know how handy you are so can't suggest addl steps other than have someone check it out for you.