Battery/low power light

[DangerRangerA1-6]

My battery light has been on for a while and I can't find the source of the issue, getting ready to drive about 10 hours and don't want to be dead on the highway. I've replaced the alternator and battery and have already checked wires for loose connections / exposed parts. I'm just lost and frustrated at this point. Any help is appreciated, thank you.

Edit: problem has been resolved. Thank you to everyone who replied

 

[Cees Klumper]

Too late for you probably, but thought I would report my experience on swapping alternators / low voltage warning light of last Saturday.
It started with me hearing a 'new noise' coming from the engine when I dropped off my wife at her yoga class early in the morning. When I got back home, I diagnosed the sound coming from the alternator (hold screwdriver against body of alternator while running, other side to ear: yes, grinding noise).
Went online to find new alternator in stock, found a Duralast Gold at Autozone 8 miles away.
Took out the old alternator and confirmed bearing was bad as expected, lots of axial play also. Mind you, it was still charging fine.
Stopped by Jiffylube place on my way to the Autozone to ask them to use their impact wrench to take off my old pulley, as the new alternator comes with a serpentine belt pulley and my Bronco II has a simple V belt. They were kind enough to do it, no charge. Luckily it was not seized up.
Picked up new alternator after confirming mounting points and plug connections were same as old. Stopped by tire place to ask them to use their impact wrench to take off the new pulley and put on my old one, which they were kind enough to do, no charge.
Back home, installed the new alternator.
Fired up the engine, and initially the voltmeter showed charge was fine, needle in the middle as with the old one. Revved up the engine for good measure and suddenly the needle dropped to half and charge light came on. Alternator faulty? Removed it, checked if the connections were good, pulley was on tight - everything was fine. Installed it again, still same problem.
Back the 8 miles to Autozone, swapped the $150 Duralast Gold for a $129 'regular' Duralast (only one they had in stock - I needed the truck later that day to trailer another car to Santa Monica from Long Beach so could not lose any time). While there I also bought a $120 impact wrench so I could swap -again- the pulleys myself, rather than keep bothering nearby garages to do me this favor.
Got home, unpacked the impact wrench only to find it was a pretty heavily used one. Oh well, it did do the job.
Installed this second new alternator and this time perfect result.
Went back the 8 miles to return that impact wrench. I would have kept it had it been new, but since I already have a battery powered one (in the storage in Santa Monica was I was trailering the other car to) and it was Autozone's defective alternator that caused me to buy their impact wrench in the first place, I decided to let them have it back. They were good about it all.
So after about 4 hours, three 16-mile trips, I finally had a shiny new alternator that seems to be doing fine. It's much quieter also, the old one that was in there since I bought the truck 3.5 years ago, had been making some noise all that time, I just didn't notice until it kicked it up a notch.
After this experience though, I think I will try to find me a new Motorcraft one, put that in and keep the $120 Duralast as a spare unit ...

 

[lil_Blue_Ford]

Duralast usually seems to be ok, but I have heard of them failing out of the box. Back when I worked for them, we would test the old starter or alternator, then test the new one to verify it was working right. Then the customer got the new one. Saves a few headaches sometimes

 

[DangerRangerA1-6]

Too late for you probably, but thought I would report my experience on swapping alternators / low voltage warning light of last Saturday.
It started with me hearing a 'new noise' coming from the engine when I dropped off my wife at her yoga class early in the morning. When I got back home, I diagnosed the sound coming from the alternator (hold screwdriver against body of alternator while running, other side to ear: yes, grinding noise).
Went online to find new alternator in stock, found a Duralast Gold at Autozone 8 miles away.
Took out the old alternator and confirmed bearing was bad as expected, lots of axial play also. Mind you, it was still charging fine.
Stopped by Jiffylube place on my way to the Autozone to ask them to use their impact wrench to take off my old pulley, as the new alternator comes with a serpentine belt pulley and my Bronco II has a simple V belt. They were kind enough to do it, no charge. Luckily it was not seized up.
Picked up new alternator after confirming mounting points and plug connections were same as old. Stopped by tire place to ask them to use their impact wrench to take off the new pulley and put on my old one, which they were kind enough to do, no charge.
Back home, installed the new alternator.
Fired up the engine, and initially the voltmeter showed charge was fine, needle in the middle as with the old one. Revved up the engine for good measure and suddenly the needle dropped to half and charge light came on. Alternator faulty? Removed it, checked if the connections were good, pulley was on tight - everything was fine. Installed it again, still same problem.
Back the 8 miles to Autozone, swapped the $150 Duralast Gold for a $129 'regular' Duralast (only one they had in stock - I needed the truck later that day to trailer another car to Santa Monica from Long Beach so could not lose any time). While there I also bought a $120 impact wrench so I could swap -again- the pulleys myself, rather than keep bothering nearby garages to do me this favor.
Got home, unpacked the impact wrench only to find it was a pretty heavily used one. Oh well, it did do the job.
Installed this second new alternator and this time perfect result.
Went back the 8 miles to return that impact wrench. I would have kept it had it been new, but since I already have a battery powered one (in the storage in Santa Monica was I was trailering the other car to) and it was Autozone's defective alternator that caused me to buy their impact wrench in the first place, I decided to let them have it back. They were good about it all.
So after about 4 hours, three 16-mile trips, I finally had a shiny new alternator that seems to be doing fine. It's much quieter also, the old one that was in there since I bought the truck 3.5 years ago, had been making some noise all that time, I just didn't notice until it kicked it up a notch.
After this experience though, I think I will try to find me a new Motorcraft one, put that in and keep the $120 Duralast as a spare unit ...

Thanks for the reply man, figured it out about a week later. There's an in line relay that's connected to the wiring between the alternator and stater that goes bad and causes the battery to not charge