horstheld1
Mercedes M Klasse auxiliary battery issue
Summary of the thread
A 2014 Mercedes M Klasse displayed an auxiliary battery error, causing sluggish engine starts. The issue was suspected to be related to the auxiliary power system not charging the battery properly. It was suggested to test the battery voltage and consider professional diagnosis due to potential complexities. Ultimately, a workshop confirmed the auxiliary battery was faulty, and replacing it resolved the errors and electrical issues.
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4 comment(s)
horstheld1 (community.author)
I have not tested the voltage of the auxiliary battery myself. Where is this battery located in the vehicle, and can I access it without specialized tools? I am apprehensive about delving too deeply into the car electronics myself.
manuelschmitz6
Given your apprehension about car electronics, and the symptoms you're describing, it's probably best to take it to a workshop. A weak auxiliary battery can affect engine start and other systems. It really does sound like the battery is not holding a charge, or is simply kaput. It's worth getting a professional diagnosis to avoid causing further damage.
horstheld1 (community.author)
I took it to a local workshop, and they confirmed that the auxiliary battery was indeed faulty and not charging. The repair cost was 290€. Replacing it resolved all the error messages and electrical malfunctions. Thank you for pointing me in the right direction!
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MERCEDES
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MKLASSE
manuelschmitz6
Sounds like a classic auxiliary battery failure. Is the car struggling to start, or are other car electronics acting up? These batteries don't last forever, and a weak one can cause all sorts of weird issues with power management. Have you tested the voltage of the auxiliary battery?