jessicawagner8

Mercedes B Klasse auxiliary battery issue

I'm officially losing it with my 2011 Mercedes B Klasse gasoline engine. I've got 122617 km on the clock, and this auxiliary battery thing is driving me nuts. The speedometer keeps flashing an error, and when I hooked it up to a diagnostic tool, the error memory was full of battery-related codes. Plus, the engine feels sluggish when starting, and honestly, the car electronics in general seem wonky. I'm pretty sure the auxiliary battery isn't charging, but I don't know where to start. Is this a common Mercedes thing? Any ideas before I end up selling a kidney to pay for repairs?

4 comment(s)

Sounds like classic battery failure symptoms. The auxiliary power system is crucial for many car electronics. Have you checked the battery voltage? A simple multimeter test can give you an initial idea of its condition.

Thanks for the quick reply! I don't have a multimeter, but I could probably borrow one. Where exactly do I test the voltage on the auxiliary battery? Is it the same as testing the main car battery, or are there any special considerations? I'm a bit of a novice when it comes to car electronics.

While you can test it yourself, given the electrical malfunctions you're describing, and your lack of experience, it's probably best to take it to a workshop. They can properly diagnose the charging system and confirm if it's just battery replacement or something more involved.

You were spot on! Took it to a trusted mechanic, and they confirmed the auxiliary battery was toast. Battery replacement and labor came out to 290€. Ouch, but at least the error messages are gone, and the car starts like a champ again. Thanks for the advice!

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