[dgonz609]

(Update): Replacing the amazon brand alternator with a remanufactured Bosch alternator solved the no charging issue.


Hello, i need some help here, i just recently purchased a 2008 e92 335i with 84k miles, the seller replaced the alternator in march of 2023 with a replacement from amazon, but shortly after the battery would not charge. i was able to start the car off a jump and drive fine until the battery would die again. So, i replaced the battery, water pump, and thermostat. I am able to start the car without a jump now, the battery reads 12.18 Amps as well as the alternator but continues to drain the battery, not sure where to go from this, any suggestions would be much appreciated.

[Tambohamilton]

Alternator should be outputting about 14.5v with the engine running. 12.2v is fairly weak for the battery; 12.7 is more like 100% charge.

I strongly recommend you get bimmergeeks protool, or INPA/ISTA and a trustworthy cable, so you can check for fault codes as well as other diagnostics.

[dgonz609]

This is what i’m getting, the fan one is because it’s unplugged.

[lowrydr310]

Sounds like a bad alternator, it's not charging. What's the voltage when the car is running?

It's possible that the new alternator failed. I had this happen to me on another car, failure after 3 months. Stick with a reliable brand, Valeo or Bosch, whichever is OEM for your car.

[e91Owner]

If the voltage is reading the same with the battery and the alternator, you’re not reading the alternator at all. It’s just the battery, meaning the alternator is bad.

The codes just confirm the same.

[Tambohamilton]

Alternator is on the BSD line (LIN bus), and could be knocked out by a bad IBS? Similar to n52 water pumps. May be worth disconnecting the IBS and checking errors again?

Certainly sounds like a bad alternator though.