Same problem here Gary~

The vacuum actuator that controls the center vents is the hardest to get at. Its replacement can only be acheived by removing the dashboard. I didnt want to do this when mine failed, so i have learned to live with it. Instead, the flow will be directed to the front windshield vents, hey~ something Mercedes Benz never invented but should have on these cars. Defog the front windshield and have A/C in the cabin at the same time!