Alternator charging, then not charging
Shortly after starting the car, the alternator gauge drops to less than 12 volts and the idiot light comes on, then a minute later it's back up to almost 14 volts?
I have a new battery and I have tested both the battery (running & not running) as well as the alternator output while running. The battery tests out perfect but the alternator only shows about 13.4-13.6 volts after the motor has been running for a few minutes. Connections are tight and everything seems to work fine but the fluctuating gauge is what I can't figure out.
Thanks for any help.