Mercedes Benz repair: air conditioner, mercedes benz 300e, antifreeze coolant

Question
i have a 1992 mercedes benz 300e and my air conditioning doesnt blow cold air, now i added the air coolant gas 2 times now, it works fine for a couple of days and then stops and i checked for leaks but i didnt see anything
and i added antifreeze coolant too

Answer
check to see if its blowing out of the center vent if not your duovalve maybe shot it is on passengerside looks like 2 electrical round sliver cylinders with a plug on them . Take off the passenger wheel cover make sure the line grey that goes to the a/c line isnt broke typically they bust by the plastic check valve add a new libne if all is ok take of duovalve with 8 pt 4 mm internal head then look at the plungers a l;iitle antifreeze will come out so do it while engine is cold you will then see where your problem is otherwise if all is good there email me back to geta code reading using your stereo