I went through 3 altnernators after my original one failed. The first I returned to Napa because it was squeky. The second failed after a day and I got the "charge system fault" and the battery voltage dropped and the battery would not charge. The third from NAPA passed their test and pepbopys altnerator test but even though autozone didn't have that same alternator they tested it and told me the voltage regulator was bad. the battery was not being charged. however when i would accelerate hard fro1 first or second gear the voltage would rise and stay steady. I was going nuts. I didnt want to deal with the pcm blah. I thought it may be the lead wire coming off the alternator but a friend tested it and said it was fine. I cut it anyways about a foot back since it was corroded looking and used a butt connector to add fresh wire, but still nothing with the voltage.
long story short, after spending hours and hours reading these corvette forums and ls1 forums I took a chance and ordered a voltage regulator from ebay for 50 bucks. I swapped it out from the alternator NAPA had sold me and it fixed the problem instantly. I called napa and told them. they offered a refund which made me mad because i had tried that but they wouldnt because it tested fine on their machine. all they could do was offer me a discount on the next purachse. Just sharing my story in case there is anyone out there that went through this alternator issue.

 

I've had so many bad parts/experiences while using NAPA parts I simply don't go there any more. For the last 10 years or so, I only use OEM parts, right down to the oil filters.

--Wag--

 

I've had similar experiences with auto stores and off-brand parts. I deal with people who sell me OEM parts based on my VIN!

 

I wish I could do the same unfortunately I'm fresh out of college and spending 700 bucks for a new alternator was out of the question. Though ironically I would have probably racked up that money and more on diagnostics and replacing other suspect parts -_- now I'm dealing with a chirp/ squeak that I can't identify.

 

My chirp was a bad Harmonic balancer, lok at it while its idling and you can see the wobble. My advise is go with solid HB 25% underdrive pulley. Read my nightmare on my page and you can see why to go to solid HB instead of stock 2 piece...