C220 that will start without OVP in place? Sorry guys but you are going to have a hard time convincing me of that one as it supplies the engine ECU with power (I dont have a wiring diagram in front of me but this is true of the 94 and 95 models and would be very supprised if it was changed for 96).
I have to agree with tkamiya about getting the heck out of there if the technicians at the dealer dont know what an OVP is. I would not be supprised however if the service advisor does not.
I have replaced many overvoltage protection relays causing a c220 to not start. If it is bad it will normally start if you smack the relay with a screwdriver or something. Another tell tale sign is that the Check Engine Light will not come on during cranking but that can be caused by a faulty ignition switch as well.
Look at the side of the OVP. If it was made in Austria...replace it weather its bad or not. Ones that were made in Germany or Hungary are generally OK.
Mercedes Benz Master Tech
ASE Master Technician
Owner of "Behind the Star Inc."