1991 CRX Si. I finally had to replace the original alternator (201k miles) when it would no longer charge the battery. First I replaced it with a supposedly rebuilt Denso unit from an Amazon vender. It didn't work correctly and wouldn't charge the battery. Bought a Duralast Gold from Autozone (yeah, I know!). It seems to charge, but the light still comes on at low RPM, though not at full intensity. It's brightest at idle, probably about half intensity, then slowly dims and goes out completely passing 1700 rpm. My guess is this one is bad, too, but wanted to see if anyone has any ideas what this could be. If it is another bum alternator, can anyone recommend a good replacement? Original Denso alternators seem to be extremely rare, and I'm having bad luck with rebuilds. For the record, I've also checked and cleaned the grounds and replaced the main relay, too.
Thanks!

 

Few questions out of curiosity come to mind, how old is the battery itself? If it's 7 years or older, probably could use a new one. Did you swap the pulley off your old alternator on to the new one or did it come with one - were they the same diameter?