1992 400E. I have a fried alternator field wire at the alternator. I have tried to determine what color it is and where it comes from (where it originates), but I have a physical disability that will not allow me to lay on my back and reach up well enough to be able to track this small wire. I plan on, after I replace the alternator (might as well, the one that is in there is what? 24 years old), simply running a new wire from the point of origin to the field terminal on the alternator. Does the field wire require a small amount of "impedence" such as a small light bulb between the 12v+ source of origin and the field terminal on the alternator to "excite" the field of the alternator?
So, I need to know the wire color and where it comes from.
Thanks, my friends.

Hi your small wire will originate from inhibitor switch for nutral start on gear selector .The picure is not for Mercedes but the same idea. Go to Gogle put in Mercedes W124 Maintenance Manual Index -W124-Zone .com Then pick your engine from list .

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Although somewhat difficult, we may see that it is not impossible to mistake the starter motor circuit for the generator (aka, alternator) circuit.

The excitation circuit [D+/circuit 61] is blue, 0.5mm, and originates at the charging indicator bulb in the instruments. The bulb is of about 1-2W, and the other side of the bulb is powered through the key switch.
In MB cars the blue D+ wire from the alternator often passes through a separation binding post on the RF inner fender. and then enters the chassis harness. If the damage is confined to the engine harness, replacement will be relatively easy.

Thank you, Frank. Optimusprime's reply had me confused (although he was kind enough to also reply to my question).
So, you are saying that the (+) side of the bulb is coming from the start switch and the (-) side of the bulb is, in fact, the field wire for the alternator? And, this wire, the blue wire, sometimes arrives at the "binding" post on the inner right front fender, so that I could, if this is the case, simply replace this wire from the binding post to the field wire spade push connection on the alternator?

A bit of semantic clarification may be in order: The whole energizing circuit, including the bulb, blue wire, and binding post, are on the positive side. The "upstream" side of the bulb is the key switch side, the "downstream" side of the bulb (and blue wire) connect to the field of the alternator.
The word ""start"" has been placed in quotes because the bulb circuit is NOT in the starting circuit. It is energized when the key is in the RUN position.

The bulb circuit reaches a ground through the alternator field when the alternator rotor is NOT turning. When the alternator rotor reaches operating speed, the + voltage at the D+ terminal very nearly approaches chassis voltage, hence the potential across the bulb is ~0, no current flows thru the bulb, and it is not illuminated.

Fantastic, Frank. I really understand this system now that you have explained it. Thank you. Now I'm going out to my garage and see what I can accomplish. I MAY BE BACK!

Long rider i am sorry .I was looking for the starter circuit ,i do know why. I had been reading a post about this starter motor, some place and it was on my mind that it was a starter.