My instinct is to replace the alternator and give that a try, but I am loathe to toss parts at something. it charges the batteries OK, I put a digital voltmeter on it and they do not track fast enough to show this flicker, but the voltage tracks along as expected. No I don't have an oscilloscope. If I toss a $200 alternator at it and the problem does not go away, it is not the end of the world. I m hoping somebody has seen this issue and can lend some insight.
Don't know your exact condition, but did you check the switch terminals/wire ends for over heat/poor contact/ loose terminal rivet condition? Have dealt with the flicker issue with older Petes and FLR's several times. It'll drive ya cuckoo till ya wiggle the right wire or loose terminal and figure it out. Just a thought.
It is really steady, the frequency. I just don't know if there's another regulator in there besides the one in the alternator.
Does it do it without it running. If you take the alt belt off does it still do it ?
No, key on it doesn't do any flickering. If I pull that serp belt the alternator is coming right out of there because that's the hardest part of changing the alternator lol. It sits right up top in front on that engine.