Same problem here. I had a dimmly lite coolant light that would lite whenever.

I bought a replacement coolant level senor at the dealer ($26)and installed it this afternoon in 10 minutes. I used my FatBoy oil drain can to suck the coolant out of the overflow tank so I could get the sensor out. Neat thing was I sucked out a lot of that brown gunk that had built up, especially where the sensor is located.

-Mike
1995 E320 75k