To add to Peter's remarks.....

Pull and examine your brushes first. New ones are about 1/2 inch in length.
If yours are significantly less, a new set could give you added boost.

How to do it:

- Elevate front of car. Ramps are nice.
- Brushes in your case come off the bottom of the alternator. Two(2) phillips screws hold them in. Remove and exmaine. If worn, buy new ones and plop them back in.

It takes longer to setup for this job than it does to remove and replace the brushes. Very easy task.

__________________
Mike Murrell
1991 300-SEL - Model 126
M103 - SOHC
"Fräulein"