Thanks ALL -
I appreciate the info and help ... I pulled the side cover off and looked at the rear reservoir and saw ... OMG WTF!!!??? (see pics below) ... apparently the previous owner didn't find this an important thing to mention before the 150 mile ride home when I bought it!?!?
He attempted to "fix" the broken res (i'm assuming he broke it by trying to loosen the fill cap) with rubber epoxy and a hose clamp.
Anyway, good thing i just picked up an almost complete parts bike the other day - pulled the res off that one and replaced... so far - no more light. Going on The Patriot Ride tomorrow and feel a LOT better about the issue now.
Took me 30 minutes to pull both reservoirs and replace the damaged with the good. Kinda proud of myself never having done that specifically before lol.
Thanks again everyone - this alone was worth the $12 membership fee