Natural interior air coming in car

[dubadaddy]

I have a lot of natural air coming into my 1990 300CE with all comfort buttons in the off position. I have removed the radio for repair and the ashtray. There is air coming in those areas as well as natural air coming in through the vents towards the doors and some coming through the defrost vents.....is there a seal or something that I can replace?

Seems as though it should be tighter as not to let in heated air during the summer and cold air in the winter....

Thanks in advance.

Sorry, messed up the title!!

[Jer]

I imagine this only happens when the car is in motion. At first two potential issues come to mind:

1. There is a vacuum leak for the fresh/recirculated air flap vacuum element. The flap is in the recirculated air position when vacuum is present.
2. There is a problem with the pushbutton unit or the switchover valve block causing there to be no vacuum at the fresh air flap, which allows fresh air to enter the cabin when you are driving (dynamic pressure forces air through the heater box).

These are fail-safe features to ensure you at least have heat in the event of an electrical failure in the pushbutton unit, or if it has been removed for repair. The mono valve is open when de-energized.