Thanks. Well, the coolant level never did go below the 1/2 way mark, but then it started coming on on my first trip out of the day after the engine was warm like if I would pull from a stop on a slight grade, but later in the trip, even on the steep part of my driveway, it would not come back on. If I would take the car out on a second trip, the light would not come back on at all.

I did go ahead and pour more coolant in it to get it above the 1/2 way mark. As mentioned, it has green coolant in it so I am soon going to change it out - probably not until spring though. The coolant I added was Prestone. On the bottle it read, "add to any color coolant, all makes, all years, all models". Its more like a yellow or very light green color. I thought it was safe to add it in. Strange that coolant such as this claims to be for ALL makes and ALL models, yet many say not to use it in a Mercedes.

I have read and been instructed to only use MB coolant or Zerex.