The voltage drop from the defroster is certainly suspect to pulling too much current for some reason, but the underdrive pullies are what really catches my attention. Is this a racecar/street car? If it is on the street then how much time do you spend idling? If you spend a fair amount of time in traffic then ditch the pullies even if you didn't replace the alt pully. They slow down the alt, which limits how much current they can put out but the current demands on it have not changed. This causes it to get a little hot, and then on top of that it is designed to cool itself while its turning so slowing it down reduces how well it can cool itself. If you have a racecar or is just not kept at idle much they can add a few hp while not hurting anything but on a car that does idle a lot, no good.