Mercedes V Klasse Diesel Battery Issues

Your battery sensor assessment is plausible. Weak starting and flickering lights suggest a charging system problem. The voltage sensor monitors the battery and tells the ECU. If the sensor is off, the ECU might not adjust the alternator, causing undercharging. Have you tested the battery voltage at rest and during operation? That could clarify the sensor's accuracy.

I haven't done voltage tests yet, but I agree about the ECU. Can you explain how to do these tests, including what's normal for a healthy battery and what deviations would mean the voltage sensor is bad? I want to understand this before taking it to a shop.

Think of the battery as a reservoir and the voltage sensor as its gauge. A healthy battery at rest should be around 12.6 volts or higher. When the engine runs, it should rise to between 13.7 and 14.7 volts. If the voltage stays low even when the alternator is running, that suggests a sensor issue. If the sensor gives the ECU bad data, like a fuel gauge reading full when empty, the system won't compensate. You could test this yourself, but modern cars often need special tools that a workshop has. It might be best to get their opinion to confirm the sensor and replace it. A repair should be around 315€.

Thanks for the thorough explanation. The fuel gauge analogy made it clear. I went to a shop, and they confirmed the voltage sensor was bad. They replaced it, and the charging system is working now. It cost 315€, just like you said. Your help was invaluable.