Alternator problem in a 99 Chevy Silverado?

[Canyon]

I have a 1999 Chevy Silverado 1500 4x4 V8 5.3L Ext Cab Short Bed
Today, I will be putting my 6th alternator in it

Somebody tell me why

The amp is pushing enough, but the regulator inside keeps saying it's bad. I've taken it to the Chevy dealer, I've taken it to my uncle who was an auto electrician, and I've taken it to my mechanic, nobody can figure it out

Does anybody have any ideas?

I replace it, it works for about a month, month and a half, then the battery light starts coming on and off, I take the truck in ,and the alternator is bad, again.

Thanks!
I put an alternator from Napa, from AutoZone, from a used parts lot in California, I live in Idaho, and Chevrolet. They are all coming from different places.
It has a brand new battery in it, it's just a few months old

 

[John L]

You may need to have the electrical system tested. But one question where are you getting your Alternators from? The same place? Is this the 6th in six months? The reason I ask is our supply warehouse got a bad shipment of them they all were bad. We would replace an alternator and a month later same thing. If its not being damaged by the truck get one from somewhere else.

 

[Joe F]

try the battery maybe something a dead cell in battery causing alternator to overwork good luck