Honda Repair: 2000 Honda Civic dx, auto parts store, honda civic

Question
My car started acting like the alternator was not charging the battery so we replaced the alternator, the car continued to act this way so after searching for answers we contacted a technician who gave us some info to change the eld so we just changed the eld tonight took the alternator in to the local auto parts store had that tested it was still good. We put the car back together and the rpms and the voltage still go up and down expecially when you have the headlights on.Any ideas what this maybe, before i take it to a dealership??????????????

Answer
it sounds like it could just be grounded wrong. if there is not a good ground, your car will solely run off the battery and the alternator wont recharge it. check all the wires that are directly connected to the frame. make sure they are tight and touching good solid metal.