1995 buick century won't do anything when key is turned. Alternator is fine, battery ok.

Corroded terminals on battery When they test the battery they attach to the studs.. Remove both the ground and positive connections at the battery. clean both the terminal and the contact area on the battery, the ideal tool is a stainless brush but even a tooth brush will work. look under the plastic coating on the cables and if you have white corrosion, mix a container of baking soda and water (a couple of teaspoons of soda to 10 oz of water...put the end of the terminal into the soda water and it will neturalize the corrosion. Dry them and then spray with WD-40 Reinstall on the battery and it should be good for several more years.