BMW: Alternator Problems, alternator problems, altenator

Question
Josh,
 Thanks for the quick response.  The first time it happened last August or so.  It was late at night...the stereo started crackling and the lights started dimming and then the car just turned off.  The car worked fine for several months and then the same thing happened in December and then just the other day it happened again.  I used to use it every day, but my friend said he's only driven it a few times sinse I sold it to him.  

 I bought the car from another guy and he took great care of it and it only had about 100,000 miles on it when I got it in 2002.  I beleive you are right about the first alternator, becuase it happened in about 150,000 miles. Both times they were done I asked about the battery output and altenator output and they assured me the battery was charged and had no problems and the altenator worked fine as well.  This was the only work I hadn't done on the car, so I was relying on their word.   
My friend took it to some auto guys on post the other day and they believe the Timing belt broke, would this be a more likely scenario?
Thanks Again,
Zeb



-------------------------
Followup To
Question -
Josh,
 I owned a 1990, 325i convertable, that has had terrible alternator problems during the last 6 months.  I had it die on my twice and just sold it to a buddy in the military and it just died on him too.  So it's had 2 brand new alternators and both have died.  I talked to someone who said it may be the alternator Bushings...Got any idea's?
Thanks in advance,
Zeb
Answer -
Zeb,
 Could you be a little more specific in the details of how the car runs and dies.  What happens before the car dies, does it run fine, but the battery slowly run down until the car stops?  I need to know EXACTLY what happens when the car "dies".  How long you have been driving the car before it dies, how often this trouble happens...things like that.

 I highly doubt it would be the alternator bushings, as you have put 2 new alternators on the vehicle, and they dont wear out in 3 months.  When you removed the first alternator, how did you KNOW the problem was with the alternator and not something else?  (i.e. did you check the alternator's output?).  Have you tested any of the alternators you have taken off and replaced with new ones?  It is HIGHLY unlikely to get 2 faulty alternators in a row.  Is the wiring correct on the back of the alternators?  The first alternator isn't really shocking, I had to replace one on my 1987 Convertible this year as well.  The other two alternator's are!!!  
 So I'm taking it that this has only happened 3 times right?  Are you the original owner of the car? In the ammount of time you owned the car, had this problem been consistent or did it just start after the first alternator failed?

 I'm thinking that the original (factory) alternator finally wore out (not unusual) and the replacement was wired wrong or a CHEAP replacement.  And the same for the second one.

Thanks
 Josh

 Thanks Zeb, get me a little more Info and I'll try to help from there.
 Josh  

Answer
Zeb,
 If the radio went staticy and the lights dimmed, it's a sure sign that the alternator/battery is shot.  The car usually slowly dies, and it's not an abrupt stop like if you turned the key off.  I've had the same thing happen, once on two different cars.  

 Just so you know how the system works, the battery powers everything on the car.  Like a flashlight, the battery will eventually run out of charge.  On a car you have the alternator to replace this spend energy.  In most cases the battery is used to start the engine, and the alternator takes over to provide enough power for the car and to keep the battery charged.  Alternators should produce ~13+ volts when running.  You electrical system is a 12v system so the extra energy keeps the battery charged (in a simple explanation).  So if the alternator dies, you are left running on the battery and like the flashlight.... you will eventually stop.  On the other hand, if your battery fails, you are stuck running on the alternator, but this will leave the battery drained, so you cannot restart the engine.  
 Either one is happening to this car.  I would like to say that the battery is fine since it will crank every day.  I would also like to say that the alternator is fine, since it's only a few months old.  So I would tell your friend to find a different brand of alternator, one with a lifetime warrantee and use it.  If it dies... then he gets one free.

 without physically looking at the car I cannot help with diagnosing WHY it is doing this, except that the wiring might be hurting the alternator some how

 Hope this helps,
 Josh