You could check the resistance across each element of the reg/rec. The Haynes manual for a 600 Fazer '98 to '01 offers no help with this, saying you need to take it to a dealer. Do you have a Haynes manual for the '03 that gives the info?
Reg/rec went on my SRAD last week and the Haynes manual for that has this:
http://www.flickr.com/photos/97669713@N02/10909052556/#
Reg/rec went on my SRAD last week and the Haynes manual for that has this:
http://www.flickr.com/photos/97669713@N02/10909052556/#