New Alternator Problem

So I threw a new alternator into the dart, the old one was making an awful noise and wasn't charging worth a damn, so I pulled out the old one and threw this in there.

http://www.summitracing.com/parts/TFF-7509RCSP/

Well I went to fire it up tonight for the first time after the install, and the gauge showed it was draining, as if there was no alternator connected. I'm not sure what the problem is now at this point. I went and looked and the alternator and it was spinning right there while at idle, everything is connected, but for some reason it isn't showing on the gauge now, where even the old busted one was showing activity at least. Any suggestions?