Deep in the dash. Do you have the 124 CD-Rom? It would give enough info to diagnose the problem and maybe enough to fix it.
I have never replaced these servos myself. I only do diagnostics. We put all the servos in when we do an evaporator as some of them are next to impossible to change without removing the dash. Maybe Donnie can help here; I know he has done this a few times (bg).
Owner 24 bay BSC
Bosch Master, ASE master L1
26 years MB technician