Dead Alternator, bad diodes
 

I bought an '01 X5 with 100K on it a few weeks ago. I had two occurrences of the Trans Fail Safe in the first few weeks. Probably why it was for sale in the first place. I researched that problem on this site and recognized that it was probably the alternator, but it just kept going. Over mothers day it left me stranded an hour from home with a dead battery. At least now I knew for sure what the problem was.

After removing the alternator, I brought it to an auto electric shop which rebuilds starters, alternators, wiper motors, you name it. They replaced two diodes in the alternator for a cost of $166, apparently there are 8 of them. I had it back in the X5 in an hour and the problem appears to be corrected. Who knows if this will permanently solve the issue, but it was cheaper than a new alternator.

Obviously there is no warranty, so I will update this if I have more problems in the future. Maybe this info will help someone elese.

i had mine rebuilt by novastar for 166. all is good. good luck with the outcome