Mercedes-Benz has been producing the E-Class, for almost twenty-five years. The executive sedans produced by this German automotive giant are known the world over with superior handling and luxury features. The W211 is a popular model in the series even though it sometimes does cause problems for its owners.
One issue that W211 drivers have encountered on occasion has to do with undue drainage of the battery which could be caused by a faulty alternator. Some owners have experienced trouble getting the alternator to turn over, especially if the vehicle had been sitting for several days. A trouble code has also been known to appear prompting the driver to check the generator.
One theory that may account for the trouble signal is that the car is continually running diagnostic tests and if it doesn't finish the tests during the time the engine is engaged, it will restart the next time the car is running. This doesn't explain the drain on the battery, however. There are many electrical components on vehicles today, so there could be any number of motors that are providing undue power to drain off of the main battery. This would be an issue that would need to be explored by a professional.
If you are experiencing issues with your Mercedes-Benz W211, either with unexplained battery drainage or a faulty alternator, you should take it in to your nearby German import technician and have them look at it. They can do a complete diagnostic test and isolate the problem. They can also provide you an estimate of all repair and replacement costs associated with the issue.
Search for a local, independent Mercedes-Benz repair shop with Mercedes-Benz mechanics that have dealer-level expertise at a fraction of the expense.