Weird random A/C Blower venting to window defrost
 

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? :mad:

Does it do this right after acceleration ?

Airflow to the windshield is the default setting. If it loses the electronic control or its vacuum supply you will get air to the windshield only. Lots of possible failure points but electronic failures are not as common as vacuum leaks in the system.

That is why I was asking about acceleration... Could be a vacuum pod (am sure they still used those damned things in a '98).
But, it won't hurt to look in the engine compartment for loose/cracked vacuum lines.