I have a bmw 2001 330ci convertible which had the alternator replaced twice in a month and half.the mechanic is claiming that there is an electrical problem and he cannot figure it out and to go to the bmw dealership.although he replaced the alternator he says this problem will occur again. please advise.thanks.when alternator is down obviously the battery starts to die as well.

It seems like something is draining your battery while the car sits overnight. causing the battery to get weaker and weaker putting stress on the alternator making it fail prematurely. the dealership will do a paracidic drain test where they'll find out what is draining your battery while your car sits overnight. it could be a bad module somewhere that's staying on when it shouldn't be.