Just in case someone else is up against the same thing: After remaining incredulous as to how a replacement sensor can output the EXACT SAME bad values as the original, I thought that maybe in handling the new and the old I had accidently reinstalled the old (bad) one. Well , operating under the principle of "the job ain't done till it's done twice," I crawled back under the dash and swapped out the two sensors and wouldn't you know it I still got a reading of 93 F for a stone cold car in a 65 F garage. I repeated the exercise but this time left the ACC diagnostic on the 05 code and to my chagrin, it continued to show 93 F, even with the sensor unplugged! So now I started getting real suspicious and poked around under there only to find a second senor, which caused the 05 code to show "open" when I disconnected it. Eureka! When I had asked for a "evaporator temperature sensor" the MB parts guy had given me the wrong sensor!! I had noticed that it looked a little different from the picture on the parts site, but the pictures are sometimes of a generic part, the label said "heat exchanger sensor" and I figured that an evaporator is in fact a heat exchanger. Moreover, since the first sensor I pulled out of the airbox matched, it never occured to me that I was monkeying with the wrong sensor. Lesson learned. Everything seems to work now.