The other day a alternator malfunction code popped up but then disappeared, I ignored it. So then the next day I drove it around no issues but then the code popped up again at night. Do I need a new alternator? And what are some ways to check if it’s my alternator or battery? Thank you to anyone that responds, your help is greatly appreciated.

 

See Is My Battery Bad? - 5Series.net - Forums.

 

Yup it’s my alternator. My headlights would also be dim but once I revved up my car they would get brighter and I heard a whine. So I guess I have to buy a new alternator. Thanks for your help

 

Or have it rebuilt. Sounds like the bearings gave out. When rebuilt, they usually replace the bearings, brushes and regulator.

 

Bearings last a very long time. If it's a Valeo, you can with some searching find a new regulator/brushes set for around $50. The brushes in particular wear out over 100K miles. Takes some searching, but look around alternator supply companies.