My62 does this too. I replaced the alternator with a rebuilt mopar from Advance and also replaced the defective mechanical regulator with an electronic one early this year. When I start the motor I get a lot of bouncing on the amp gage until the rpm’s get up. Then it settles down on the midrange line. At idle it still bounces and made worse when I use the lights. It actually shows a discharge at idle with the lights on. Following this thread with interest…