I have a 300m 20002 with about 198k miles
really good car, everything works except the ac controler

i'm looking for some help
I'm just a hobbyist.I have a 300m with AC issue
The ac does work, but only comes out the defroster
I have some temp control but nothing else (mostly high/low)
I can not change where the air flows
the ran motor is stick on high the fan control does not work
it appears that the controller on the dash board does not work
(the display and controller by the radio)

So I went to the junk on got a replacement and installed it
it does the same thing

I had a friend use a diagnostic tool.
not sure if he really know how to use
claims the the dampers work.

Please help .
Thanks Glenn

 

Did you try a "re-calibrate" procedure ?
Set temp to 75, press and hold 3 buttons simultaneously, top row last two, bottom row 4th from left. Hold until the unit blinks and release. Then done will show a code.
If the fan is stuck on high it is likely the bolwer module has failed