I just snagged a nice condition 84 300SD to augment my 300 SD collection (not really, this makes 2). However, after starting, the alternator/battery light stays on for 10-15 seconds. My other 300Sd doesn't do this. Any ideas? Battery going bad? Alternator going bad? Glow plugs?

83 300 SD 176K
84 300 SD 222K

gawlbpd,

I would agree that is not normal and the item in charge of making the light go out is the voltage regulator. I would look there first, and to really look you have to take the uniti out of the back of the alternator. I think there are some good threads that describe how to do this, so try a search. It is not hard to do, only two screws hold it in, but it might be hard to get to with a turbocharger in the way.

When you get it out, look at the brushes and if they are worn down to little nibs, that is your problem. In your search you will find results where guys actually replace the brushes for a few bucks. I have never done that but I think you can get a new Bosch unit from Fastlane for less than $50. They used to be a lot cheaper and it has been a while since I did one. Good luck, Jim

__________________
Own:
1986 Euro 190E 2.3-16 (291,000 miles),
1998 E300D TurboDiesel, 231,000 miles -purchased with 45,000,
1988 300E 5-speed 252,000 miles,
1983 240D 4-speed, purchased w/136,000, now with 222,000 miles.
2009 ML320CDI Bluetec, 89,000 miles

Owned:
1971 220D (250,000 miles plus, sold to father-in-law),
1975 240D (245,000 miles - died of body rot),
1991 350SD (176,560 miles, weakest Benz I have owned),
1999 C230 Sport (45,400 miles),
1982 240D (321,000 miles, put to sleep)