If there's any short or inadequacy in the Small Wire System (Blue),like say a
connection loose or corroded [Or something Wrong with the Dash Idiot light]
the Alternator will not make any power.
[no "Excitation" circuit]
The X10/4 is just a Positive Transfer Block with Two sides.One for the "Power"
and one for "Signal". The Left side Screw (As you face the Firewall)with the Blue wires is the Alternator "Signal" side of the transfer Block.
The Right side with all the heavy-er cables and Two posts is for Power.
[And Both of the Threaded posts are connected by the plate they are embedded in.]
I've learned from others here that MB's are Plagued with Barely adequate
wire Gauging.
A one Volt loss on such a small cable run is significant.
See gsxr's Alternator upgrade tutorial:
http://www.peachparts.com/shopforum/showthread.php?t=53236&highlight=alternator+upgrade
You'll note he replaces the Tiny Blue signal wire with a larger AWG.
Favorite Alt innards R+Rs:
http://www.oichan.org/mods/alter/alter2.htm
and
http://v12uberalles.com/Alternator_Bearing.htm
(Thank God you've not gotta go through THAT to get to the Alt. !)