Your air problem is somewhat similar to what is happening to my daughter's car. 'mbdoc' suggested the problem might be the freeze sensor on the evaporator. I have not got around to looking in the service manual CD to see how much work it is to get to the freeze sensor. If I can't fix it I will take it to the local dealer.

Here is the link to my earlier post, if you're interested:

CLK320 Strange Air Conditioning Problem

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