Alternator Bosch or OEM Mazda

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.

Lucky for us, the Alternator was in fact faulty (it was a Bosch btw) and that the previous owner replaced it a few months prior, meaning it was still under warranty.

Bosch is a great aftermarket option.

Yes, if it was from an OEM supplier to Lexus or the auto industry, such as Denso (1/3 owned by Toyota/Lexus), AC Delco, or Bosch, but I would not buy a mystery brand, especially not a rebuilt, because I don't know how much they get rebuilt or tested.

I wasn't crazy with the AC Delco (GM) alternator conversion when I used it on my MGB engine. The Bosch ones seemed to be a little better designed and easier to convert, plus they looked simmilar to the Lucas ones.

Bosch rebuilt alternators are like $175 online. Lots of people experienced low quality rebuilts. Have people had good luck with Bosch rebuilts?

I had a bosch alternator in my Mark 2.. 8valve motor. I noticed the battery was not being charged. so instead of dealing with the voltage regulator or brushes etc, b/c the unit was old I decided to go with a brand new one.

I when my original alternator failed in my 540i/6, the replacement rebuilt Bosch unit would produce 13.5-13.7v for a while after the car had warmed up, then would gradually fall to less than battery voltage. Running the A/C and revving the engine at stoplights would keep the battery light from flickering, but eventually, it would show full symptoms of a dead charging system.