Electrical problems after replacing the alternator

My alternator went out so I replaced it. After replacing the alternator my low beam headlights won't come on but my high beams work fine and my head unit won't come on. The new alternator does not seem to be charging the battery. If I drive it for about a half the battery starts to die all the lights dim and it won't shift out of first gear. All this happened in a day. I drove it to work this morning perfectly fine also I thought it might be a bum battery. So I took it to AutoZone had it charged and tested the battery is good. I thought it might be a bum alternator they sold me. So I took it back off had him test it in the store and it passed and the fuses for my low beams and my head unit are good.