I had basically the same problem as Patrick suggests. Freon level was never low and once the sensor was replaced, everything was right with the world again. Mercedes put out a technical bulletin about this issue, so it's a known problem with these climate control systems. The bulletin basically says to replace the sensor before you do anything else, reprogram the system and see what you've got. In my case, everything returned to normal and the system has worked well for six months now.

I sure wouldn't spend a penny doing anything until that sensor is right.

Len
'99 E300TD 68,000 miles