ABS Light/Rough Idle Quirk
 

On my 91 every now and again, when I start the car, the ABS light will come on and the idle will be rough. Then after a few seconds the light goes out and the idle is immediately smooth. Just a minor quirk...any ideas what's going on?

Might be voltage regulator and/or brushes on their way out.

Alternator replaced 70k miles ago.

It is the overvoltage protection relay behind the battery. Will have a red top with a fuse.

I'd second that. OVP relay on it's way out.

I would also suspect the OVP.
If you have a soldering iron, try reflowing the main pins contacts to the OVP board and see if that cures it. Lots of write ups on how to do this and fairly easy.

Believe it or not, I had several of these lying around in my random parts bin! So swapped it out.

Interestingly, the old part number 201-540-32-45 is no where in the MB parts system. The guy at the MB parts counter was telling me it's not an MB part...when I was holding it in my hand!

Anyway, hopefully that does the trick. Thank you all for pointing me in the right direction.