Thank you for your response. My mechanic wrote it up as a purge switch over valve. The old valve at the time was clicking. He told me that I could change it myself. I repaced it with P/N A 000 470 22 93. The valve is in the front of the w/s washer reservoir. Mercedes also calls it regeneration valve. As far as the power to the valve, I don't know if I have 12V and I don't hve an instrument to test it.