Seat Leon Diesel Weak Starts and Flickering Lights

I had something similar with my Seat Leon. Weak battery, flickering lights, all pointed to low voltage. Have you checked the battery charge? A defective battery sensor can definitely cause these symptoms, leading to a car battery not charging correctly. Battery maintenance is crucial, especially with these diesel engines. It might be worth investigating the sensor itself before assuming the entire battery is failing. Do you know how to use a multimeter to check for voltage drops?

Voltage drops? How would I check that?

A multimeter can measure voltage at various points. Checking the voltage at the battery terminals while the engine is running will tell you if the alternator is providing sufficient charge. Low voltage readings, especially when compared to the expected output, indicate a problem. Since the symptoms persist, I suggest a workshop visit for a proper diagnostic. They can pinpoint the exact cause of the low voltage and verify if it's the battery sensor itself. Continuing to drive with this issue can cause further damage.

Yep, it was the battery sensor. Replacement set me back 315€. Thanks for the advice.