Battery Light Problems

Im having trouble with my 99 Alero. Back in August battery light comes on, bought a new battery for the car and replaced the alternator because the Alt failed. 3 months go by and the alt seems to have failed again same battery light same problem battery 12+ volts while engine off, and when engine running slowly losing voltage. Replaced Alt again 2 days ago battery at14 volts while running everything seems ok then today the battery light comes back on. Havent had a chance to chek voltage on it again. Im at a loss could it be another bad alt out of the box or is there some other problem that could be causing the alt to go bad or just something else all together????
its an ac delco alt

Welcome to AF!!

Make sure that all your connections are good and clean the wire going to the alternator. If it is a plug in type coat the posts with dielectric grease before you plug it in. Also make sure the battery is at full charge before starting the car. The wire connected to the back of the alternator should also be cleaned before installation. Also make sure not to install the alternator with the battery cables connected. This can damage the alternator.

It is possible to get bad alternators right out of the box but it is doubtful. I would also check and make sure all grounds are good as a bad ground can cause charging issues.