Acc/ccu 1990 560sel
I've read the archives and, unless I missed one, I can't find reference to this ACC problem.
The AC compressor activates and operates at any temperature setting of the temperture wheel if any pushbutton on the ACC unit is engaged, except for the "O" button or "EC" button; for these last two buttons, the AC compressor does not operate.
The AC compressor does not cycle on and off with the three other button settings but runs constantly. The temperature wheel setting does not control temperature and hot air blasts out from the side vents and footwell vents - no air from center vents under these circumstances. Evidently the hot air overwhelms the chilled air from the AC. BUT, if the temperature wheel is turned to the full cold detent position, the side vents and footwell vents immediately close, and cold air blasts from the center vents (and rear vent).
I changed the monovalve insert; no change. If temperature wheel is turned to full hot detent, AC compressor continues to operate but hot, hot air blasts from side vents and footwell vents.
I can't follow the logic of what is happening. Evidently there is vacuum and the flaps operate as they should but something is signaling the ACC system to function as if the temperture in the cabin is very cold. Any ideas before I order a new ACC control?