Fuquad; (nice name =)
Just took a look in the repair manual...
It doesn't specifically state that the circuit is an active low, but since there is only one wire going to it I can assume that it is.
Simple test, unplug the switch. It is located just under the drive pulley towards the front of the bike. You should be able to pull the wire off the switch. (for the love of god, be careful) if light goes out then you have a bad switch. Just to be sure, take a chunk of wire and manually ground the wire you just pulled off the switch. That should cause the light to change as well. If that works, just change the switch and you should be golden.
If that doesn't work then you will have to follow the wire thru the bike and find out where it goes and look for a worn or pinched wire. You are looking for a tan/yellow wire all the way from the switch, goes to the fuse panel then "y's" off to the instrument cluster.
Let us know where you get.
(and thank you Fidosol)