Transmission light problems

[MBClass]

About a week ago the check the transmission fluid level light went on in my 1997 C230. It would go off for short periods of time but it would light up again. I added more transmission fluid and the light was always on. I bought a dipstick to measure the fluid level from the dealership and it turned out there was too much fluid in the transmission. I drained the transmission and added the correct amount of the fluid. The problem is that the light is still on. After changing the fluid I took it out for a test run and after a while it turned off. On my way home it turned on again. Can anyone tell me why this is happening?