So I did the DIY, and everything started going as advertised. About ten minutes into my drive after having installed the new voltage regulator (did it without removing the alternator), everything was going well. Then all of a sudden I check my battery and it's back down to 12.1-12.2V after having been 13.8-14.0. I stop the car and upon re-starting it.. The dreaded red battery light is back. I installed a new Duralast 49-DL exactly a week ago.
Any help would be greatly appreciated.