So I got a brand new alternator from Autozone, put it in a few minutes ago, crank my car, it starts, everything was fine. I've heard that a way to test the alternator on a car is to unhook the battery, if the car stays running, the alternator is just fine, if the car dies, alternator is crap. So I unhooked the battery and the car died ? Why? the alternator is brand spanking new! I also took my battery to Autozone to recharge it and test it. It was still a good batery. Anything else that can be causing this?