Alternator Bosch or OEM BMW

What brand alternator did you use? If not OE, Bosch, or Valeo, change it again.

Step up and buy a Bosch. Yes, they do fail, but the odds are much less.

Bosch is still the gold standard but not what it used to be. Don't buy cheap junk.

Stick with a high quality oem replacement alternator; VW installed a number alternator oem brands (bosch, Valeo, Hitachi, etc). My 2002 New Beetle Turbo S; had a Valeo 120 Amp unit installed, I had a hard time finding a Valeo unit, so I went with Bosch and so far, I have not any issues with it but the body of the alternator, was slightly bigger, so the wiring harness, was a bit of a tight fit.

You can get a Bosch alternator for a KA and swap the pulleys

Any time I see overvoltage faults I replace the alternator. Check the charging voltage and confirm that it's charging higher than 15.0v (it may happen only briefly under some conditions). If it is then unplug the connector from the alternator. That should default it to 14.3v. If it still overcharges then you've confirmed a faulty alternator.

B5/5.5 alternators come from two vendors, Bosch and Valeo. I've heard they're not interchangeable because of different pulleys.

Alternator. And unlike prior generations of Bosch alternators you can't replace just the regulator, which is usually what fails. Gotta buy the whole piece.

Good thing you got a Bosch instead of the duralast. I had a duralast alternator last about 2 weeks and when I was standing in line at AutoZone to return it and buy a real alternator, there was someone behind me also holding an alternator that lasted two weeks.

So, OK, ended up getting a Bosch Reman from IMC, installed it to find out it was only producing 10Volts @ idle. Took it back out, and installed an Ultima which put out 14Volts @ idle.