hi.
i have a 2009 s550 and i cant find the way to control the rear ac zone. i have no controls in the back seat and nothing in the infotainment screen.
im trying to figure out if there is something im missing or not understanding. thanks for the help

You do not have rear A/C. Few S class in the US has rear A/C. If you have no A/C controls in the back (under middle air vent), you only have 2 zone (left/right) A/C. Rear A/C is part of rear seat package, rear seat can recline.

There should be dials near the vents that you can reach back and tickle. But as jd986s mentioned, there's no Rear Automatic Climate Control unless you have the package. It comes with the Designo cars like mine, S600s, etc., or could be ordered as part of a package.

The display looks like this;