The cigar lighter trick won't work on a W210 since the lighter socket goes dead when the key is off. However, connecting a 9v battery to the charging post in the engine bay will work to keep settings. Frankly, resetting the windows (express feature), radio and sunroof only takes a few seconds.

To the OP - Your 'new' battery must be too low ( < 12.0v) to convince the ECU to go to work. Take it back out and have it charged.

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Good luck.






1998 E320 Wagon