Headlights pulsating dimming problem

1997 Buick Skylark, with new battery and alternator. Headlights and dash lights are dimming up and down in a pulsating fashion. the lights are not going out and I can see alright, but just do not have constant light stream.

Did the lights pulse before the new battery and alternator were installed? I’d want someone to test the alternator, even though it’s new. You may have gotten a bad one.