WOAH!!! 12's are only normal if ur car is off. its supposed to be mid 13's to low/mid 14'2 at idle. hondas have one big and 1 thick wire at the alternator. make sure the thick wire held dwn by the 10mm nut is tight and not touching the case of the alternator. and make sure the big plug is plugged in. if all thats in tact, ur alternator is more than likely bad. unless u got bad wiring, but unless u had previous issues its unlikely. good luck