Tom brought up an interesting point about alternator brushes.
When mine were worn to a nub, some of the dash lights came on and the car stalled. I want to say the SRS & ABS came on, but I don't really remember.
When this happened on one occasion, the car was idling poorly. Seeing the dash lights on, I decided to read the open circuit voltage with a VOM and saw something like 9v - 10v. Anyway, digging thru this sites archives, I found some hits on the alt. brushes or volt. reg. as some call it and decided to have a look.
I put the front of the car on ramps and pulled the encapsulation panel from underneath. On the backside of the alternator are 2 phillips screws holding the volt. reg. in place. Remove the screws and out comes the VR. Brushes on a new one are 1/2" long. It's been said here that the commutator ring wear inside the alt. can be so much. I cannot say what that limit is. After the 1st set of brushes I replaced wore down, I just decided to pop for a reman Bosch alt. and installed it.
If your brushes are worn, you may very well be able to get away with just replacing them. There are basically 2 kinds listed here at this sites parts facility. One is OEM Bosch; the other listed as "German". A lot of folks here have indicated that the lesser expensive German brushes did the trick.
Here's a link to what the volt. reg. looks like:
http://catalog.eautopartscatalog.com/mercedesshop/sophio/wizard.jsp?partner=mercedesshop&clientid=catalog.mercedesshop&baseurl=http://catalog.peachparts.com/&cookieid=1EQ0PTV2S1RV0MQ82Y&year=1992&make=MB&model=190-E-005&category=F&part=Voltage+Regulator