I have searched throughout the forum as well as others to solve this issue..so far no luck. 2000 Expedition, replaced alternator due to old one giving out (Alt Light on Panel). Verified with Advanced Auto the Alt was bad. Installed re- manufactured one and it cleared up the alt issue. Problem now is that all lights (interior and exterior) flicker at a rate that changes as RPM increase. Battery is one year old and reads 12.4 without engine running. Alt shows 14.1 to 14.3 depending upon load. I had new Alt retested thinking it was Voltage Reg but it passed test at Advanced Auto. Verified connections from Alt to Battery and also cleaned all connections on Battery. Thought it might be GEM but it does not come into play with headlights. Anything electrical with lights flickers. If I increase speed of fans on A/C or use power seat adjust it increases flicker as well. I still believe its Alternator but hoping someone here has more experience.

Do not want to give in and visit DEALER...he has all the JOKERS.

 

I meant to add it's a 4.6L not that should matter. I did Ohm out the alternator harness and all appears to be good. Made sure all the relays and fuses both in Junction Box and Internal Fuse Panel are seated. No water leaks that I am aware of and truck stays in garage most of the time. Have not checked Mega Fuses. I did validate solid ground between battery and chassis. Not sure about anything else. Vehicle is fine to drive but at night it is hard to focus with slight flicker in headlights and dash lights.

 

Recently bought a 2000 expedition and having the same issue. Did you ever get this resolved? I'm stumped on what it would be.