karenschwarz1
Mercedes B Klasse Diesel Undervoltage Errors
Summary of the thread
A 2019 Mercedes B Klasse diesel is experiencing undervoltage errors, poor starts, intermittent system failures, flickering lights, and weak battery performance. The initial suspicion is a discharged or faulty battery, but potential issues with the voltage regulator or alternator are also considered. After checking the battery terminals and confirming they are clean and tight, the problem is diagnosed at a garage, revealing a faulty alternator. Replacing the alternator resolves the issue, restoring proper function to the charging system.
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4 comment(s)
karenschwarz1 (community.author)
Terminals are clean and tight, I already checked. The battery is not the original, but it's only about two years old. How did your friend figure out it was the alternator? Were there specific tests he ran, or did he just replace it and hope for the best?
christophermoeller1
Ah, okay. Well, my friend took his car to a workshop to get it diagnosed properly. They used some kind of tester to check the alternator's output. It might be worth doing the same, just to be sure. Otherwise you will be changing things and hoping for the best. A workshop should be able to quickly determine if it's the charging system at fault.
karenschwarz1 (community.author)
Cheers for the advice. I took it to a local garage, and you were spot on. Turns out it was the alternator playing up and not charging the battery properly. New alternator fitted and the charging system is working as expected. Cost me 290€ all in. Problem solved.
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MERCEDES
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BKLASSE
christophermoeller1
That sounds frustrating! I'm no expert, but could it be something simple like a loose battery terminal connection? Have you checked those to make sure they're clean and tight? Also, is the battery the original one? Maybe it's just reached the end of its life. A friend of mine had similar issues and it turned out to be the alternator. How old is your battery?