Single wire small module on the back of the alternator is probably a noise supression capacitor. If it has a visable part number on it you may find it in the manufactures parts list. If you have a meter that reads capacitance you could see if it reads. Another way of identification is on a very high range ohm reading you might see the chargeup till your meter reads open or infinity. The black lead has to be disconected for that test.

The capacitance checking function is starting to show up on many cheaper meters reciently. Not a particular lot of use for the average guy but nice for checking ac motor capacitors and a few other things out from time to time. For example a lot of portable generators have capacitors and they can be failure prone.