So today i made a trip to a relatives house in my 82 ZX, going through a tunnel, straight shot, and all of the sudden all of my dash lights come on, and my voltage drops to 12-13 volts on the meter. Car is still running 4th gear 40-45mph. after 10-15 seconds, the dash lights go off, but the volt meter still reads low, like the Alternator isnt charging. A minute or so after the Dash lights go off, the Volt meter reads normal (14-15 volts). Throughout the rest of the trip this happens randomly, sometimes the dash lights just flicker for a second when the volts drop, sometimes they dont flicker on at all when the volts drop. Checked all connections that i could, and they all seem tight and secure. Alternator was replaced 10k miles ago by previous owner. No belt slipping when volts drop. Could there be a short somewhere? Bad ground?
All input is appreciated.