79 240d, the outer dash vents have adjustable twist flow control, the inner two dont.

Can the inner two be replaced by adjustables?

How to remove/install the outer adjustables? There is a thin chrome ring and wave spring washer on the outside and the vent assembly behind the dash. Appears to have four small rectangular slots in each piece. I would have expected one with slots and the other with tabs, but no. Seems the mode of failure is these slots break off the edge piece and wont hold together. How are these held together and how do you disassemble without breaking?

I haven’t been a 123 in a long time. Doesn’t flipping the center vents 90* about the pitch or yaw axis block airflow?

Sixto
98 E320s sedan and wagon

The twist flow control is a butterfly flap in the air nozzle itself. Don't know if you can retrofit the outside nozzles to the center vents but whey would you want to? The center vents air supply is controlled by the sliding lever right beneath them.

- Peter.

__________________
2021 Chevrolet Spark
Formerly...
2000 GMC Sonoma
1981 240D 4spd stick. 347000 miles. Deceased Feb 14 2021
2002 Kia Rio. Worst crap on four wheels
1981 240D 4spd stick. 389000 miles.
1984 123 200
1979 116 280S
1972 Cadillac Sedan DeVille
1971 108 280S

Because my mech says he can modify the flap somehow that will provide a significant increase in the airflow but it stays open all the time. Installing adjustable vents provides a way to reduce the flow when you dont want cold air.