My father in law has a 1993 GMC Suburban with a 350. The last alternator fried and got a rebuilt one, put it on and it will charge for about 5 minutes. After that it "cuts out" and wont charge the battery. All the connections are good, as far as I can tell, the battery is only a few months old, and the belt is new. Im thinking its a faulty alternator, but is there anything else I should look over?

Side note, I took the alternator in to NAPA to test it, it checked out ok. Since it works fine for about 5 minutes in the truck, im guessing its heat related??

 

I have replaced a "Rebuilt" alt 3 times B4 I got a good one......

 

My bet is w/ the alternator...