W220 bought in June from Mercedes: alternator broken/door control unit who has to pay?

Hi I bought first hand a Mercedes S 320 Cdi Bj 08/2003 with 87 t km at a Mercedes dealership in Austria on 14 June 2012. After 2 months the control unit broke down. According to the dealership, this is a wear part and went on pickup. I’m not paid. Now I drive to Munich with just under 200 km/h and the engine shuts down, every light goes off and servo no longer works. In the display stands light generator dekekt. Adac comes to check: Conclusion Overvoltage alternator k aputt. And this after 3 months and 8 t km. Now the Lima eig. is also a wear part… read today in the I net that the car dealership in the first 6 months does not have to prove that the defects existed during delivery. What chance do I have? What do you mean if you don’t want to take over the costs? directly turn on my lawyer. Thought you would buy a smart car and have only problems… Greeting Michel