Check the overvoltage relay.
It is located behind the black plastic cover behind the battery.
It is silver with a clear cover covering a fuse in the top.
Check the fuse.
You can test by jumping pins 87 and 30 with the relay out and see how it runs.
Look at the bottom of the relay for pin numbers.
Mercedes Benz Master Tech
ASE Master Technician
Owner of "Behind the Star Inc."