Changed alternator and the flickering stopped. Had my old alternetor checked out twice at two different Auto Zones, both times the test said alt was good . I changed it anyway with their best Alt and its a beauitful thing no more pulsing lights . Thier tester will not pick up the slight plusing from a worn alt, it showed a steady 14.5 , if youve got high mileage on your alt. mine had 140k when it started to go nuts

 

Mine did the same thing. I took the alt out to look at replacing a part and cleaned all the terminals a and reinstalled...no more flickering.