most of the MB switches that have auto down/up/open that I have encountered have two distinct positions when pressing them. One (the first position) operates the window, sunroof, etc. like normal (ie. the window moves until you release the switch). The second position, pressing the switch further, engages the auto up/down/open feature. Now, based on this information, does it feel like your sun roof switch has two positions or just one? I'm sorry, I've never been in/owned a w140 so I don't know specifically.