Mercedes GLK diesel undervoltage problem

I had similar electrical problems in my GLK. Weak starts, systems going haywire. Have you checked your charging system? An alternator issue can definitely cause low voltage and drain the battery. Also inspect the battery terminals for corrosion or loose connections. Is the undervoltage warning appearing consistently

I have not inspected the charging system directly. Where should I begin to diagnose a potential alternator issue? Is there a straightforward way to check the battery terminals for corrosion? I'm not very experienced with electrical systems

Given your lack of experience, I would advise against attempting alternator testing yourself. Battery terminal corrosion is usually visible as a white or bluish build-up around the terminals. It's best to take your GLK to a workshop to have the charging system professionally tested. A defective alternator will cause low voltage issues and can damage your battery. With the cost of components these days, it could be a costly mistake to ignore it

Understood. I appreciate the advice. I had the GLK inspected, and you were correct. The battery was defective and caused the low voltage issue. Replacing it cost 290€. Thank you for pointing me in the right direction