We just had the same problem on my son's 93 #00E. In our case, it turned out to be an easier (and cheaper) fix than pulling the dash for a bad element. If I recall how our tech explained things, after he checked vacuum response at the 3 way vac valve behind the glove box area air bag, he determined the problem was probably elsewhere: under the battery tray in our car is a vac hose which goes from the vac reservoir in the passenger fender to the firewall. This hose had cracked and needed replacement. This was a lot less expensive than if it had been a pod/actuater/whatever under the dash. I have not seen these parts and am not conversent with the exact names or location, but this inexpensive hose fixed the problem.

There are a ton of threads on the center vent problem in the archives, so try a search on these to see what others found with this problem. Good luck, and hope this helps.

__________________
John

2003 Firemist Red/grey leather SL 500
2015 Palladium Silver/black mbtex GLK 350
1987 Smoke Silver/burgundy mbtex 300E Sportline (SOLD)

Click to see 87 300E