2000 E320 4matic wagon with around 190k miles. I had issue with wipers not shutting off regardless of where I put the switch position. I checked fuses (all good) and removed covers around windshield wiper motor, then removed motor cover to check for dirt/corrosion. All looked good. Next removed entire fuse box cover under hood on drivers side apron. The cover is held together with approx 8 screws along the perimeter of the cover. Located the relays, which I suspected to be the cause. I wiggled one of the relays and the wipers stopped. Replaced relay (I had one in my spare parts bin) and all working as it should. I took the old relay apart to see where the failure was and the contacts were dirty and sticking. Just thought I'd share this info should anyone else run into this issue.