85 300CD instrument warning lamps - PeachParts Mercedes-Benz Forum

frankjnjr · #1 01-08-2008, 08:58 PM

when starting my car cold, i turn the ignition switch on, all appropriate warning lamps are on, at completion of the glow cycle, i engage the starter and start the engine. on the first cold start of the day, and only on that start, the batt, brake pad and parking brake warning lamps remain on at engine idle, and stay on until the engine idle is increased ever so slightly. the alternator was a rebuilt of unknown origin and age so i removed it, cleaned it, sanded the commutator, dressed the brushes, which were well worn but serviceable, and re-installed it. same problem. i than tested it and found out-put at 12.3v, the battery (new mercedes) less than one year old tested 87% charge. i than located a bosch alternator, not a re-built, which appeared to have been recently installed on a 300d at the local pick & pull. i installed the newly acquired alternator, cleaned all electrical connectors and ground straps etc., started the engine and the problem remained. the pick & pull alternator tested at 12.9v, again with the battery at full charge. i have searched this thread as well as the diesel thread and and been unable to find a diagnosis for this exact problem. any suggestions or ideas would be appreciated, thanks

Johnhef · #2 01-09-2008, 09:27 PM

heres the thread I mentioned last weekend: http://www.peachparts.com/shopforum/showthread.php?t=117059&highlight=alternator

unfortunatly it never seemed to resolve for me according to the thread, although I do know I fixed it somehow because it never did it for at least the last year or so I owned it (the 82 300CD). I'm almost certain a new voltage regulator did it.