The problem is fixed...by me and not the FOUR different Mercedes shops that missed it. So much for the paid professional.
The car had elect. problems....dead battery, low battery, no start, entire car going dark (stalling) during driving....no charging lite would come on, but the belt tensioner was at fault, maintaining just enough drag to keep the alternater lite off, but not enough to put enough juice into the battery. I changed the belt and tensioner and this car has run flawlessly for the past 9 months...