Mikecanfixit

Friends 06 Mustang GT 4.0. At night, lights flicker, dash lights go out, headlights go out, tail lights bright then dim and go out. Gauge warning light comes on. Car runs still. Tested the alt, showed it was good ( but that was done by Oreillys and we all know how that goes) Battery is three months old. Installed a new ignition switch yesterday. Did it again last night. Smart Junction box? Alternator? Headlight switch? Battery sounded dead, starter just clicked but in the morning the car started just fine. All this just happened over the last 3 days. Any ideas?