On this 1998 C230 I'm experiencing some weirdness with the air conditioning venting. Randomly, when the AC is running the system will switch from blowing the cold air straight out from the front (main) blower vents redirecting the cold air to blow through the window defroster vent. Then after several minutes it will be redirected back to the main frontal vents.

I don't know why the vehicle thinks the wind shield need the cold air blowing on it when I could really use it blowing on me when it's 98 degrees outside. Do you think the vehicle cares more about the comfort of the window glass than me?

Any suggestions on what the problem is other than the car doesn't like me?