why does the voltage gage at times flutter back an forth

You are absolutly correct. There is a short in the electrical system. Start be checking the battery terminals for corrosion or loose. It's lickly related to your battery or alternator. If you feel motivated remove them and have them checked. I'm not sure where else you can go to have this done for free but Firestone perfoms an electrical system check on the battery when you get your oil changed. This is done at no charge.