alternator trouble

I'm a new owner of a 2005 645, 3 months in and the alternator is shot, I also have an aftermarket battery. Should I replace both? Also should I buy the alternator and have it installed, or would it be best to go through the dealer. Does anyone know the correct cranking amps for the battery? Any info greatly appreciated.

bou645

I would not change the battery if it tests out OK. Specs are 110AH, 850CCA, 205RC and costs around $220 according to this great thread on batteries. The big problem is none of the aftermarket batteries compare to OEM on the 205RC spec which is critical since the 6ers heavy power demands.

Tischer - getbmwparts.com - charges $510 for an alternator. I would have an independent install it or if the indy can get a Bosch remanufactured alternator that would be just as good.

I have a Bosch Battery 9456178 that replace the original in May 2008 that is almost 5 years without problems, I replaced that one today with the same battery, and the old battery still working but sometimes i'm getting the active steering code or high voltage message on my radar detector.
after i connect my car to my laptop and check the codes i thought that the battery is the problem because after i have the car connected to my battery charger and diagnostic software i check the voltage and i have only 12.03 volt after few hours that means that is losing the charge and probably the cause of the error messages i get when the alternator try to compensate.

Just to add......make sure it's not just the regulator in the alternator. I originally thought I had a bad alternator and just replaced the regulator and i was back in business. Costs about $30 bucks for the regulator.

Here is a pic of the regulator before I installed it on the alternator. Maybe this will help someone out. Sorry i didn't take any pics as I swapped it out.

procedure to do an easy test for the regulator using multimeter?

Originally Posted by bouknighth

I'm a new owner of a 2005 645, 3 months in and the alternator is shot, I also have an aftermarket battery. Should I replace both? Also should I buy the alternator and have it installed, or would it be best to go through the dealer. Does anyone know the correct cranking amps for the battery? Any info greatly appreciated.

bou645

How did you check it was the alternator ? And I would check the amps on the battery now and aftermarket batteries can be good but you have to have it register with the car if not man it'll die out on you with in a year wether it's new or used because the computers on these cars know what type of battery are in the car and not to mention they hold memory too