Tell me what you think. I have a 1990 300D 2.5 with 435k on it. This has been a great car except that it loves alternators. The first time I ran into this problem was February of 2006, I am sitting at a red light and the idle starts to drop and all accessories die then the car. I have it toed to the dealership (I use to work for Mercedes) and it’s diagnosed as an alternator. No big deal, I get them to install a new (reman) one and all is well till June of 2008. I am on a road trip in Florida and get in the car and with no type of warning my battery is completely dead, no big deal I buy a new battery (Shirley it‘s not the alternator right?). No problems till I get back to NC. A week after my trip with no warning the new battery is dead. I take the car to a friend of mine who owns his own Mercedes repair shop and once again it needs an alternator. Now… August of 2009 I am on a road trip and stop for a break, try to start my car, with no warning the damn battery is dead. Mercedes road side comes out, jumps it off and I drive it home. With a full charge on the battery I have the car checked again and it needs another alternator!!! What gives 3 alternators in less than four years? In each case it’s the diodes in the alternator. All 3 where Bosch. Everything works perfect on this car. If anything ever broke I fixed it. There are no drains on the system when the car is shut off. That’s all I can think of...

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Mike

90 300D 511k
95 C280 133k
14 BMW 528i