Alternator OEM Audi or Bosch

I have only rudimentary experience working on cars, but I got the OEM Bosch for like 300 (less core return deposit after I mailed back the old core). Took me about an hour or so to replace myself.

I only trust OEM, Denso, Valero, and Hitachi. Bosch isn't too bad.

I have one. I replaced a Bosch with it. Hasn't had an issue and had a lifetime warranty.

Yes. I had one on my e39 (M54) for a long time. Probably put close to 75k miles on it before I sold it. It was the Bosch variant. No issues with it at all. In fact, it appeared to be a Bosch reman in an Autozone box. Hard to tell what the internals were but they looked exactly the same.

If anyone is curious, the 120a Bosch and Valeo alternators (rectangle ground connection) are completely interchangeable despite the statements online saying they have different pullies and mounting points. They are slightly different but everything lines/bolts up the same. The Bosch (left) is a decent amount larger in size, not sure why, but it fits perfectly with no clearance issues.

The forums are riddled with people who tried to save a few bucks & got what they paid for. The DME on an e90 is extremely fickle. DO NOT buy an alternator unless it\u2019s a Bosch.

I replaced the battery, and upgraded to an AGM battery while I was at it. The problem still wasn’t solved though.

I order a Bosch AL113MX Reman Alternator (yep Bosch reman the Motorola) since that was what was currently in there. The 81 has a big square York compressor mounted right on top of the alternator which means that to get the rear alternator bolt you better have the right extensions and you are going to do it blind. So after at lot of effort I got the old alternator out and the new one in and only then did I notice that the pulley did not line up.

Ive had a few Bosch reman failures lately at my shop as well, although they were for N52s, all bearing noise after about a year.

Symptoms: Flickering lights, and occasional hiccup start. Now battery light is coming on and staying on. When stationary battery tests around 12.5 volts. When running, that drops to 11.7 volts.