Babybenz,
I guess his thought was if the tensioner was bad he wanted to eliminate a possible problem area. That and make an extra $500.00. I spoke with the shop today and told them I had replaced the tensioner but still no AC. He went on about how since the tensioner is ruled out it could be other parts of the system or just a low charge. As far as experience with 190's, I asked the first time I took the car in if they worked on Mercedes and they told me yes. He seemed to confirm alot of the information I had read here on this site. I guess I have no other choice but to go back and have them check for leaks in the AC system and add a charge if necessary. Maybe I"ll mention about testing the system with a pressure gage as you stated so he'll know I some idea of how the system works. Thanks for you input.