BMW 8 Series Starting Issues: Battery or Alternator Fault?

Hey there! I had a similar situation with my 2020 BMW 7 Series 730d last month. The symptoms you're describing sound exactly like what I experienced, dim lights, hard starts, and error codes. Initially, my alternator was failing, but it turned out this was caused by a damaged serpentine belt that wasn't caught during routine maintenance. The belt had created a domino effect, leading to alternator damage and putting stress on the electrical system. It was actually quite serious, as continuing to drive could have left me stranded or caused more extensive electrical damage. My suggestion would be to get this checked soon, as electrical issues in these cars can cascade into bigger problems. In my case, both the alternator and belt needed replacement, plus some minor wiring repairs where the failing alternator had caused some wear. Worth getting it sorted properly rather than going for quick fixes, these problems rarely fix themselves and usually get worse. Hope this helps with your decision.

Thanks so much for sharing your experience! Really good to know about that serpentine belt being the root cause, wouldn't have thought of that connection. Do you remember roughly how much you ended up paying for the whole repair job? Also, has everything been running smoothly since the fix, or have you noticed any other issues pop up?

Hey again! Happy to give you a follow-up! Since having it repaired, my BMW's been running like a dream, absolutely no starting problems anymore. What a relief! The mechanic spotted that it was actually a software glitch causing the starting issue, not the alternator problem I initially thought. Turns out it was a consequential error from a previous repair that wasn't properly cleared from the system. The best part? They fixed it without charging me anything since it was linked to the previous work. Just needed a proper diagnostic reset and some system updates. The alternator and belt were actually fine, I was way off with my first guess! Just goes to show how complex these modern BMWs can be, what seems like a mechanical issue can sometimes just be the computer getting its wires crossed, so to speak. I'd definitely suggest getting yours checked out professionally. These electrical gremlins can be tricky to diagnose on your own. Let me know how you get on with yours, always interested to hear if it's something similar!

I really appreciate all your help and insights! Just wanted to update you, I finally got my car checked out yesterday. You won't believe it, but it was something completely different than what we thought. Turns out my battery terminals were super corroded, and there was a loose connection causing all those problems. The mechanic cleaned everything up, replaced some worn cables, and now my car starts perfectly! It cost way less than I expected, just under €200 for parts and labor. Such a relief! The mechanic was actually great too. They showed me exactly what was wrong and even gave me some tips on preventing future corrosion. The lights aren't flickering anymore, and the error code's gone. Thanks again for encouraging me to get it checked out properly. Sometimes the simple fixes are the best ones! Really glad I didn't put it off any longer.