its a 91 300E

I can't believe that when the center button is pressed its supposed to leak some air through the defrost.

When the EC button is pushed the vaccum valve has vacuum and closes all the way.

I do not have full vacuum this valve when pressed.

The whole problem is the windsheild frosting up because it will not close the valve when the center button is pressed in.

Surely Mercedes is not that stupid. Having replaced the vacuum pod under the dash, and tried a new panel, I know only one thing.....the defrost vent valve is not getting the vacuum it should when the center button is pressed, but when EC is pressed, the valve closes off all defrost air.