alternator issues?
 

we replaced the alternator in my sons 2006 325I last month. we bought a rebuilt one. the battery went dead this last weekend and we started looking around to see what is causing this.. we hear a faint hum under the engine and found that the water pump wont stop running.. the water pump was replaced by BMW a little over a year ago so we took it to the dealership and they are telling me the alternator is not communicating properly with the computer and its keeping the water pump on along with another system? is this possible and could we have just gotten a bad alternator??

Just to get on the same page here - you already replaced the alternator and nothing changed, the water pump is still running? I would check the voltage. Use this article here for help: BMW E90 Alternator Replacement | E91, E92, E93 | Pelican Parts DIY Maintenance Article.

What rebuilt alternator did you purchase? Did you purchase it from us? If the alternator tests out well it could ultimately be a faulty water pump. I have seen this before when individuals have replaced the alternator, even with a new recently installing a water pump. Yours should still be under warranty if it turns out to be the problem. Let me know what you find out.