Hey guys I have a 01 740i sport with about 63k now and i have recently replaced waterpump, radiator and hoses, expansion tank, P/S hoses. both belts. The car has been running fine but today when i went to turn it on i noticed that the battery light stayed on. I drove the car and it seems to drive fine so far. The battery its self is maybe a year old if that..Now is it possible it could be my alternator at 63k?? Or is it possible it could be something else like my belt being loose??

I am trying to avoid spending $600 for a new alternator if I dont have to.

Let me know what you guys think...thanks

1. check voltage via OBC
2. check alternator via local auto parts store

how do I check the voltage?

Follow the instructions here (you can have the key in position I, though, to avoid having to fasten your seat belt):

http://www.bimmerboard.com/forums/posts/129948

Look at "TEST NR. 09."

Should be over 12 with engine off, over 13.5 when running.

ok so this is what reading i got:

engine off UB. 11.6 V
engine running UB, 11.2 V

Whats does this mean??

And if I do need a new alternator what you guys think of this aftermarket one http://www.autopartswarehouse.com/bizshop/ymmp/bmw/740i/alternator/1999/2001.html?apwcid=L1092232221W411a241dbe70a&apwkwd=Aftermarket+Alternator+BMW+740I+1999+2000+2 001

Based on the readings you gave, the alternator is not charging at all. Very soon your battery will be discharged.
Check the connections to the alternator terminals. You may have a loose wires there.

so i went ahead and changed the alternator and everything seems fine now. This car has cost me so much money and im really thinking of getting rid of it. It just sucks because i have pretty much done everything it needs.