Alternator?

The length of the wire and the connector on the end should be able to tell you where to put it.

It's the exciter wire - it provides excitation current to the alternator - without it the alternator hardly works at all - without it the battery will go flt.

And if it falls off the battery charging light will always be off - i.e. you will have no indication that the battery is not charging.

http://rennlist.com/forums/928-forum/391880-roger-and-i-have-an-exciter-wire-question-3.html

Put it back on...
January 2015