Which climate control actuators do what? I want to disarm them in such a way that defrost is off and side, central, and floor vents are always on.

Two behind the glove box?
Driver's side near floor - floor vents.
Driver's side above floor left side of CC unit - defrost?
Top center above CC unit - central vents?

We will be happy to help you if you will please tell us what kind of a car you have.

__________________

"Buster" in the '95

Our all-Diesel family
1996 E300D (W210) . .338,000 miles Wife's car
2005 E320 CDI . . 113,000 miles My car
Santa Rosa population 176,762 (2022)
Total. . . . . . . . . . . . 627,762
"Oh lord won't you buy me a Mercedes Benz."
-- Janis Joplin, October 1, 1970

1984 300D

Sorry of course, and Whunter is correct, 84 300D.

I sorted it out.

Two behind the glove box - fresh air?
Driver's side near floor - floor vents
Driver's side above floor left side of CC unit - defrost
Top center above CC unit - central vents

Finished and now I have excellent central, floor, and side venting. The real trouble is the actuator arm for the central vents. If one wants it off then that person should;

Remove the passenger side "under-dash cover," reach up to central vent housing, remove rubber housing boot enough to get some of your hand in, open then vent plate, locate the actuator arm in the center of plate, push arm to the left (toward driver side) until the retaining clip releases, move arm out of the way, refit rubber boot, refit cover.

Of course, this is the poor man's way of getting your vents the way you want when either the a/c control unit is bad, or you have one or several actuators with bad diaphragms. If you do go this route you can reconnect everything with ease accept the actuator arm to the central vents. If you want to do that the dash will have to come off.

Yes, the center vent is a PIA. Had to work on mine a couple of times when I had a W123. W124 is just as bad if not worse.

__________________

"Buster" in the '95

Our all-Diesel family
1996 E300D (W210) . .338,000 miles Wife's car
2005 E320 CDI . . 113,000 miles My car
Santa Rosa population 176,762 (2022)
Total. . . . . . . . . . . . 627,762
"Oh lord won't you buy me a Mercedes Benz."
-- Janis Joplin, October 1, 1970