I recently started having problems with my car and I'm not sure where to start looking. Back several months ago, I had a low voltage code in my car. Put in a remanufactured Bosch alternator at the recommendation of the local Benz shop. Didn't fix it. Turned out to be the K40 relay, so in went a new one. That seemed to fix the issues I was having. Within the past week, I started having problems with the lights on my dash fading and flickering. Everything seemed to be OK as long as I wasn't running the heat, my headlights, radio, etc. I went by a German repair shop and they load tested my alternator. I'm not sure what measurement they were using, but they told me my alternator was only putting out 50 of whatever, when the normal amount should be 100. They recommended replacing the alternator. At this point, I did not replace it. I went by Advance Auto and they said my alternator was putting out 14 volts and it was fine. Well, then the problem got more prominent and I started having drivability issues at night when I was using my headlights. What would happen was the dash lights would fade, my headlights were flashing, and two lights (ABS and ESP? I was in freak out mode, so I can't swear which lights they were) would flash, and my check engine light would flash. They would all flash in harmony and with each flash, my engine would feel like it was breaking. Almost like I was hitting the breaks then letting off in approximately 1 second interval pulses. I was talking to a mechanic that does not really work on Mercedes and he said it sounded like it was low voltage to him. What could cause low voltage? Even though my check engine light was pulsing with all the other lights, it never stayed solidly lit and there were no codes stored. The engine pulsing has now gone away and the check engine light is not on, but I can still see my dash lights "sparkling" very faintly. Last night on my way home, we had on the radio and my window was cracked. My daughter reached over to roll up my window, and the lights flickered and the radio cut out for a split second.