Undervoltage in the vehicle: experiences and solutions for BMW 5 Series

Hi, I had a similar problem with my 2013 BMW 3 Series a while back, it sounded just like your description, especially with the low lights and battery. In the end, it was actually a low voltage problem. My mechanic had to check the entire vehicle electrical system because the whole circuit was affected. It was a very time-consuming problem, but fortunately no irreparable damage. Nevertheless, I would advise you to have it checked as soon as possible. Waiting too long can only make the problem worse. Hope this helps you!

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Hey, thanks for your reply and your input. You've just confirmed my fears. Not pretty, but if it's more than that, there's not really much I can do. Can you remember how much the whole thing cost you? And nothing has followed since, right?

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Hey, sure, I can still remember it well. The whole thing cost me €750. The problem was related to the contact resistance in the supply line, and that was a real money-eater. But since I went to the mechanic, the undervoltage problem has definitely been fixed. So far, nothing has come up again. So, yes, the repair was expensive, but it was worth it in the end. Hope this helps you!

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Oh, man, that's pretty expensive... But I guess there's no point in ignoring it. Better to fix it now than have bigger problems later. Since I have the same symptoms, a contact resistance could be the problem for me too. Thanks for sharing your experience with me. I will now make an appointment with my mechanic. Maybe I can negotiate a better price. Thank you very much for your help!

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Greetings, I have also had problems with the power supply. In my case, however, it was fairly easy or very quick to find out. On my car, it was simply the alternator/generator that was defective. This was replaced and the V-belt was also replaced, since then everything has been fine again.

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I have bmw f30 330e and for my vlcar broken kle modul (which are under the seat). New one price is 1700 euro. But i found much much cheaper solution. Take out modul and friend which work with microsheme fix problem. Change jumper and another small things. Price was 300 job and another parts and 150euro for take out and put back modul to the car. Its working as new :) if need pictures i can send you what change.

Can you tell me how I can check the alternator? Does it work with a simple multimeter or do I need other measuring tools?

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Hey, yes, normally a simple multimeter is sufficient here. If you simply set the multimeter to "V" and connect it to the positive terminal of the battery and to a "ground point" or to the negative terminal of the battery, you should be able to measure a voltage of around 14 V when the engine is running. If the voltage is below 12.5 V, the alternator is usually defective.

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Thank you Benny! I actually only have just under 12V when the engine is running. A new alternator has been ordered. I will have it replaced at the weekend by my friend Schauber.

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Hello, thank you for your diagnostic feedback on my late 2015 BMW F21 LCI Pack M 118D. It's true that a few times, I encounter a timid start on the car but once I've driven a few kilometers, the problem no longer recurs. I've noticed it when I start the car after it's been stationary for a few days. My battery is still the same as when I bought it. I think the battery has something to do with it. Thank you for your feedback.