Sometimes, the battery can go, causing a big load on the alternator, causing the alternator to seem bad.....or even go bad.
If the battery is 5 years old, or more, I would replace it.
On my '96 3.8L, there is a fuse "T" in the engine compartment fuse / relay box that can blow, causing the alternator to not work.....So I would also check that. It is one of those mini plug in fuses.