Get ready to get lectured about buying it at advance, not by me but......... My so called 1 day old motorcraft alt is bad out of the box. Funny thing though is that I had a pep boys reman alternator in my last truck for over 8 yrs

Just have them test the battery and alt for free. only takes a few min

Yeah the alternator went out on my way from New Jersey to North Carolina and I could see the store from the highway so I kinda didn't have a choice on where to buy from

Is it just you headlight dimming, or the dash lights and radio also? I would also be suspect of a grounding issue if the alternator/batter test good.

It's just headlights radio and dash are fine
I haven't got a chance to test it yet

I hear ya. You can't always wait 3 days or more from a part from rock auto. I've had good and bad luck from advance, autozone etc

I usually go to orileys just because their warehouse is closer than the store and I can just go pick it up from there if it's not in store

I get the same random dimming with my headlights only.. Been doing it for years.. It doesn't happen all that often but it does happen.. I almost think it's normal....

Yeah I feel like most people wouldn't notice it it will dim a bit and stay dim for like 10 min the get brighter for a while

When it happens to me it just dims for a second or 2 and then recovers.. I usually only notice it on longer rides.