I have a 1990 190E 2.6 and my ac blew out hot air from the defroster and side vents bec my valve was not working. not sure if the cars or the same in design, but what i did was take the valve out and manully pulled the tab to close it, then i tried to blow water through it while i held it shut...the wwater went right through it, so what i did was take to pennies and taped them over both sides of the valve with double sided tape to the back of the pennies and placed it on the opening (its a perfect fit), then i secured that with electrical tape, so that coolant didnt pass through it. a/c works fine and i noticed at least a 95% difference in coolness without the heater blowing the same time as the ac. only 95% difference bec its summer where i live at now and the temp is always like 115-120 degrees and the blk leather and blk exterior never cool down 100%