To Jim Anderson's point.

The volt. reg. is underneath the alt. 2 phillips screws are removed and out it comes. Slip in a new one and reinstall screws. I say this assuming it's the problem. New VRs have brushes that are 1/2 inch long. Yours may be much shorter. If they are, try one of the $15 German VRs that you can get from this site. They used to be about $15...maybe they gone up a few bucks.

It takes longer to setup for this than to actually do it. A really easy DIY job.

__________________
'91 300-SEL