On Sunday, I put the correct Continental belts on the PS pump and the alternator.

Left off the ac and air pump just to see if they were part of the problem.

So far belts are fine. They sit in the sheaves deeper. I ran all the electrical accessories I could and turned the wheel hard right to hard left, all while varying engine speed. Belts didn't flutter at all. Drove it for three days ow and all ok.

I think the entire issue was using belts that were not of correct cross section. So, lesson - don't buy belts for your Benz at local parts stores in an effort to save time.

Alas, I now have a high idle. I've performed a search here and will be checking vacuum hoses first, then the idle control black box.

Thanks for all you comments and guidance.

__________________
Thank You!
Fred
2009 ML350
2004 SL600
2004 SL500
1996 SL600
2002 SLK32
2005 CLK320 cabrio
2003 ML350
1997 C280 Sport