Mercedes M Klasse Rain Light Sensor Problem

I have an M Klasse and had similar light sensor and rain detection issues. Does the light sensor think it's always dark? Check the sensor for damage or debris near the rearview mirror. Clean the windshield around the sensor.

Thanks! Were your symptoms the same? Besides damage, what should I look for when checking the sensor? Is there a way to test it?

Yes, same symptoms: headlights always on, wipers not adjusting, dimming issues. I didn't test the sensor. A workshop confirmed the bubble issue, dealt with it, and recalibrated the sensor. Car electronics can be tricky, so professional help is best.

You were right! Bubbles under the gel pad were the problem. They replaced the pad and calibrated the sensor. Everything works now! It cost 62€ Thanks for the help!