I bult one of the below alternator test cords to bypass the wiring and charging light to see if the alternator works.
Someone over on benzworld is the only other person I know that also built one.
I cut off an alternator connector when I was at the Junk Yard. It comes apart so you can service the wires.
Post #13 has a picture of the actual cord.
http://www.peachparts.com/shopforum/diesel-discussion/379680-no-charge-idle.html