Drove the Mini up to Charlotte from Atlanta last night. Hit some patches of very heavy rain. When it got really wet the fan belt started squealing and I would see a substantial voltage drop. The lights and wipers were running, so it was under high loads as well. Reading on the Mini forums there are three potential causes. First is loose belt, second is failing alternator bearings and the third is failing water pump bearings. First two are pretty quick fixes. The third would be tougher. So, are alternators fairly generic and what are the odds that I could walk into a typical auto parts stir and get one for the Mini?