I am helping a friend troubleshoot his 1991 Mercedes 420SEL. It will
not start. We determined it is not firing (no spark from the coil).
We have been told it is either the ignition control unit or that
something is triping the overload relay. How can we determine which
one is the case?
Is the overload relay normaly energized and become de-energized when
there is a problem? Or Vice Versa.
Any help would be greatly appreciated.