Flickering or pulstating Headlights

Cleaned out all the connections in the headlight plug, installed new switch, and grounded switch housing tab to body, nothing changed. I just can't figure it out. Thanks
I recall 2 examples where the issue was the very last piece that one might suspect.... Ground cable from engine block to battery. Most notable story was the 68 Nova that belonged to electrician. No need to type all that here.