for future reference, the fan that sucks air over that sensor in the overhead console is located in the dash. You have to pull out the lining of the glove box and you will see it on your lower right, near the vent. It is a small little thing. With the key in position 2, it should run fairly strong. If this is bad, the climate control will exhibit what you are experiencing. But, I will say, my 420 does the same thing, and my fan is good. I think the thermostats are on the cooler side. I find that putting the dial in the white area, right before the blue, is a nice setting and the fan will eventually drop to medium.
Hope this helps.
93 300D 2.5 Turbo, Black/Palomino 273K
09 E350 Black/Black 41K