Hey guys, I'm sorta at a dead end on my truck dropping voltage as the rpms's increase. It's to the point where when I reach 2500rpm, the voltage gauge dips to around 11 volts, but as soon as I let up, it starts back to charging. When starting, it charges fine and I even show 14.60 on both of my DVOM's. After warming up, voltage is steady around 14.3-14.2.

Things have been done and changed;
Converted 2G to 3G alternator.
1ga charge cable with 175amp megafuse.
Cables are in pristine shape!!! Just went through all of them.
Checked the brushes in alternator, they look fine and even have room for the paperclip to hold them in place.
Motorcraft voltage regulator. No aftermarket junk.
No crappy wire splices. All grounds in good shape.
Battery fully charged.
Belt is nearly 9 years old, and its Motorcraft. It has roughly 18,000 miles on it, but does have some cracking. I have a new Gatorback belt suppose to be here Tuesday.
Belt tensioner is only 6 years old and have plenty of room for adjustment, so its good and very tight.

I know 2 years ago, when I had same problem, I changed the brushes and it did fine, but all together, they only have maybe 9,000 miles on them.

Do I just need to take the alternator In and let them test it?

Thanks for any help!

 

It's the belt !

 

That's what I'm thinkin too, so I hope the new one does it!