BMW Z3 Electrical Gremlins: Terminal 30 Mystery

I had a similar issue with my 1997 BMW M3 last season. The symptoms were identical, slow cranking, battery warnings, and system voltage drops. Took it to my mechanic and after diagnostics, they found multiple problems: The main battery terminal connections were corroded, but the bigger issue was the alternator starting to fail. It wasn't charging the battery properly, which led to the constant discharge warnings. The repair involved replacing the alternator, cleaning all terminal connections, and installing new battery cables. While they were at it, they also replaced the voltage regulator since it was showing signs of wear. It was a serious job that took about a day to complete, but it fixed all the electrical issues. If your Z3 is showing similar symptoms, I'd recommend getting the charging system tested first. The Terminal 30 circuit is crucial as it's the main power distribution point, and any issues there can cause exactly what you're describing. Since fixing mine, I haven't had a single electrical problem. Just make sure you find a shop that specializes in German cars, it makes a difference.

Thanks for sharing your experience! That's really helpful since it sounds exactly like what I'm dealing with. Would you mind telling me roughly how much you ended up paying for all that work? Also curious if you've had any other electrical quirks pop up since the repair? My baby's been a money pit lately, so I'm trying to budget for this fix properly.

Hey, thanks for asking about the costs! I'm happy to report it was actually much simpler than my initial repair. After seeing a BMW specialist last week, they diagnosed it as primarily a battery issue, it was heavily discharged and starting to fail. They thoroughly checked the Terminal 30 circuit connection too, which turned out to be the root of those annoying warnings you're also seeing. The total came to 290 € for parts and labor, which was honestly a relief since I was expecting much worse based on my previous electrical repairs. I'm glad to say everything's running perfectly now, no more warning lights, starts like a charm, and the Terminal 30 continuous plus interrupted message is completely gone. Just a heads up though, if you're seeing the same symptoms, definitely get it checked sooner rather than later. These electrical issues can snowball if left too long. But from my experience, it might not be as expensive as you're fearing. My car's been running like a dream since the fix last week. No new quirks or gremlins to report!

Thanks for the reassurance! Finally got my car back from the shop today. You were right about getting it checked quickly, turns out my issue was a bit different though. The mechanic found that my alternator was actually fine, but there was a nasty corroded connection at the Terminal 30 junction and a failing voltage regulator. The repair bill came to around 400 €, a bit more than yours but still way less than I'd feared. They cleaned up all the connections, replaced the voltage regulator, and gave everything a thorough check. Got to say, the car feels completely different now, starts up instantly and all those warning lights are gone. Honestly, such a relief to have it sorted. Been driving it for a few days now and it's running perfectly. Thanks again for sharing your experience, it really helped me prepare for what to expect and gave me the push to get it checked out properly instead of putting it off!