If your SLK is experiencing a low-coolant warning light coming on at times, be sure that your dealer replaces BOTH the coolant level sensor AND the washer-fluid level sensor. The sensors are in a series circuit with each other. Meaning that if either one goes bad, it could affect the other. Sort of like Christmas tree lights, if one goes out, they all go out. A bad coolant-level sensor could turn your low-washer fluid light on, and vice versa.