Here is the whole deal from a tech!
been there and done that!
When the cars wear, they draw more current. IE the fuel pumps and the blower motor and the aux fans use a little more current when old than when first built. I have seen where the original alt is just barely adequate to run all of these at once. To CURE the problem, I just installed the higher amp alt from a diesel and soldered the two output wires to one and installed a ring connector on the end to adapt to the higher amp alt.
I have done 3 this way with no comebacks! Two had big amps for the stereo that drew alot of power.
ASE CERTIFIED MASTER AUTO TECHNICIAN
SERVICE MANAGER FOR 14 BAY FACILITY
MERCEDES SPECIALIST 8 YRS
PARTNER IN MERCEDESSHOP.COM