I have an 04 C230k Sedan and have an issue with my A/C. At highway speeds, the A/C only produces minimal cold air. As soon as I get off the highway, it will kick out extremely cold air. Makes long trips painful cooking in the south. Any idea why this is happening? I will be taking into the shop since it is still under warranty but hope someone else has seen this so I do not get the run around from the dealer. Thanks!