If they can't duplicate the problem, I would probably have them sit the car out in the sun at idle with the air conditioning off. Let it run for an hour then drive. I have had to get many cars to fail in this way!! Persistance pays off in this buisness. If they still can't duplicate, just have them replace the crank sensor and let us know if that fixes the problem!!
ASE CERTIFIED MASTER AUTO TECHNICIAN
LEAD TECHNICIAN FOR 14 BAY FACILITY
MERCEDES SPECIALIST 8 YRS
PARTNER IN MERCEDESSHOP.COM