BMW Battery Symptoms Point to Major Electrical Failure

Hey there! I had nearly identical issues with my 2013 BMW 3 Series diesel last winter. Same symptoms, sluggish starts, dim lights, and those annoying system failure warnings. Took it to my regular shop where they did a full electrical diagnosis. Turned out my alternator wasn't charging the battery properly, and the battery itself was shot. The alternator had some worn-out brushes that weren't making proper contact. Had to replace both the alternator and battery. It wasn't just a simple battery issue, the faulty alternator had been slowly killing my battery over time. Pretty serious stuff since it could've left me stranded if I hadn't addressed it. The starter motor was also showing signs of stress from all the hard starts. Not saying this is exactly what's happening to your 4 Series, but given the similar symptoms, it's worth getting both the battery and charging system checked properly. Make sure they test the alternator output under load, not just at idle. Hope this helps.

Thanks for sharing your experience! That sounds exactly like what I'm dealing with right now. Quick question, 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 electrical quirks pop up? Just want to get an idea of what I might be looking at cost-wise and whether this usually sorts out all the issues for good.

Hey again! Great to hear back from you! Actually, my situation turned out to be simpler than I initially thought. I took it to a mechanic last week, and thankfully it wasn't the alternator causing trouble in my case, just a heavily discharged battery that needed replacement. Total bill came to 290 € and that fixed everything. Since the repair, all those undervoltage warnings have completely disappeared. No more dim lights, no more system failures popping up, and the car starts like a dream now. It's running perfectly smooth, just like when I first got it. I know in my first message I mentioned my alternator issues, but looks like I got lucky this time around with just needing a battery replacement. Should've probably waited to get it properly diagnosed before assuming the worst! Sometimes the simplest solution is the right one. If you're still having those issues, definitely get it checked out soon. Battery problems can cause all sorts of weird electrical gremlins, but they're usually straightforward to fix once properly diagnosed. Let me know how it goes with yours!

Thanks for the update! I'm actually relieved after hearing your story. Just got back from my mechanic today, and guess what? It was pretty much the same deal, just needed a new battery! Cost me about 300 bucks in total, including labor and diagnostic fees. The funny thing is, I was stressing so much about potential alternator problems and major electrical issues, but it turned out to be way simpler. The mechanic explained that these modern BMWs can show all sorts of crazy warning lights when the battery's on its way out. My car's running like new now, starts right up, all the lights are bright and steady, and those annoying system failure warnings have disappeared. What a relief! Really glad I didn't waste time and money going to the dealer, who probably would've charged triple for the same fix. Thanks again for sharing your experience, it definitely helped me feel more confident about getting it sorted. Sometimes we just overthink these car problems, right?