The temperature controller is the heart of the ACC system. It decides when the AC compressor should be on, how much to flow through the monovalve and how strong the blower should blow. The push button unit is just a user interface.

Bypassing means moving over most of the AC innards from a 240D.

Make sure you're getting +12V to one of the monovalve terminals before tearing into the temperature controller.

Sixto
91 300SE
87 300SDL
83 300SD