Greetings to all. I am a long time lurker and first time poster. This resource has proven extremely helpful over the years for which I am very grateful. I am currently facing an AC problem that has me stumped that I hope someone here can help me with. The AC on my '98 SL500 recently started acting up - it sometimes blows warm air when it's supposed to be cooling and vice versa. Additionally, I have noticed impressively large puddles of condensate forming after shut down. After researching this site, I learned of the diagnostic capability that is built right into the climate control module (!) and after pushing a few buttons I thought I had solved the problem. Because the evaporator temperature shows 93-95 degrees prior to a cold start, despite ambient temperatures in the 60's, and never gets much below 70 while driving, I figured that I had a bum evaporator temperature sensor - right? The inappropriate temperatures that were blowing out of the vents at times was the control unit's effort to compensate for what it perceived as inordinately warm air coming off the evaporator while the large puddles of condensate was the sign of an iced-up evaporator thawing out. Well, I put a new sensor in and to my chagrin, I get the EXACT SAME temperature readings. I figure the chance of getting a new sensor that is bad is slim but the chance of getting another bad one that outputs the same bad numbers is next to nil. So my questions are as follows: Would a bad connection somewhere between the sensor and the control module cause the temperature to read high? (I would have thought extra resistance would cause a thermocouple to read low.) If so, are there any other connections to look at besides the connector to the sensor and the connector to the control unit? Are these sympoms an indication of a bad control unit? (All the other values seem to be about right). Is the replacement of the control unit with a new or rebuilt one a plug-and-play operation or does it require a hook up to the MB computer? (The listing for the unit on the parts site says that it requires "coding".) Does unplugging the unit to check/clean the connectors require such "coding?" Is it possible to check the viabilty of the sensor? (I wasn't able to get any readings with my multimeter, but the fact that the sensor does show a range of temperatures, albeit wrong, as the evaporator cools down indicates that some sort of a signal is being generated.) Any suggestions/advice would be greatly appreciated!