I recently bought a 1998 SLK with only 57k miles on it. During the inspection I found the low coolant light was on, but in the 30 minute test drive the temp level stayed low, and there were no leaks. I could see the coolant flowing in the front resorvoir.
I then joined the SLKWORLD forum and begin looking for reasons for this. I found several good articles with the search forum. I used a three step approach to fixing this problem.
1. check all of the fuses in both fuse panel locations. Engine area and side of dash. Result: Everyfuse was good, and I at least confirmed there were no other problems, but the light stayed on all the time.
2. Ordered a coolant sensor and replaced it. Very easy to get at, and replacment was not difficult at all. Took the old one out, put the new one in and.......low coolant light still on.
3. I searched some more and found the windshield washer sensor is also on the same line as the coolant sensor. One member posted a good writeup about this. I ordered the part last week, it came in on Friday. On Saturday I took the wheel off, the liner out, and repalced the washer sensor in the plastic container. Another easy to get to sensor. Before putting everything back together I started the car and.....SUCCESS.
NO LIGHT ON. I then put everything back togheter and celebrated my success with a well deserved libation of my choosing.
Thank you Search Engine for the threads, and thank you to the Forum Members for posting such a good write up on trouble shooting this problem.