ChesapeakeLimo

I have a 2010 S550 with four-zone / rear-seat climate control. The vents for the left-rear passenger are all blowing/venting HOT air. I've tried moving the temperature setting from LO to HI, HI to LO, powering off and on, and tried changing settings from oth the rear control panel and the front COMAND controller. No change. Pretty much stuck on hot for the left-rear seat zone.

Wondering if anyone has experienced a similar oroblem and resolved it? On any other car I'd assume its a stuck blend door or actuator motor, but with the complexity of these models, I wanted to rule-out a computer calibration issue if that is something to consider?

Can anyone tell me where the blend door is for the rear seat climate control with certainity and/or provide a schematic?

Also, I understand that on some other models there is a way to access error codes from the climate control system. Is that possible on the W221 and if so can someone provide that procedure?

ChesapeakeLimo

...I might also mention that the COMAND controller knob is scalding hot and the keypad and console top is very warm. (This may be because I closed-off the vents to the left rear seat to keep the heat from flooding the left rear passenger zone.)

ShansAMG

Not sure if you have had this fixed by now as its a few months ago but I just recently bought an S500 2010 model and had the exact same issue. It turned out to be the Heater Change Over Valve which is located in the front wheel well behind the cover. took 2 days to get to this conclusion even though diagnostics pointed to it. Not an easy accessible valve but a competent garage could sort it. Part cost me £300.00 plus labour... Hope you got yours sorted...it had me baffled!!

Speedriven1

Most likely, as mentioned above its the heater change over valve. Pretty common failure!