You Must Hook Up the Chassis Wires EXACTLY as Mercedes intended.
(No Substitutions!)

I'd take them both back to the Zoo and make it their problem!
The Alternator they sold you is NOT the correct one for your Chassis!
[On the "Fresher" Alternator (On the Left in your Picture) the Left hand
post for a ring terminal connection HAS NO CABLE ON YOUR CHASSIS
TO CONNECT TO it!

[I suspect the smell of Fried Wires will prevail shortly]

__________________
'84 300SD sold
124.128