My car is a 2000 SS with the 5.7L V8. In January the original alternator failed and my troubles began. I purchased a brand new Duralast Gold (Not a Reman) from Autozone and switched it out myself. Once I got it put back together the new alternator had a deafening electrical whine to it that was unbearable. After doing research everyone said auto parts alternators were junk and sometimes it took 4-5 trys to get a good one. I returned it to Autozone and not wanting to do the job over and over again I decided to have the original alternator rebuilt. The first rebuild lasted 5 months before it failed. I had it rebuilt by the same place under warranty again in June. Now while driving around I'm having an issue where whenever the car hits 3500 RPM the voltage drops from the half way mark down into the red and my check gauges light comes on until I let off. Once I slow down the voltage goes back to normal.

Is this a sign the alternator is getting ready to fail again? I don't want to spend $350 on a new GM one and having now removed and replaced the alternator 3 times I'm tired of doing the job. What would you guys recommend as a good aftermarket alternator that will last 13 years like the original one?

 

What kind of condition is your belt and tensioner in? The belt can be slipping at and above that rpm which wouldn't allow the alternator to do its job.

Parts store alternators are fine, reman'd or new. Yes, there is the occasional bad one out of the box or shortly there after, but most are good okay. You can ask to have them tested before you buy them just to ease any doubts. Most auto parts stores have machines to test alternators and starters.

To me, it sounds like something else is causing the alternator fail prematurely if you've gone through that many.

 

^^^ Could be the belt is slipping, or some wiring is shorting out when the engine moves on its mounts under heavy loading. Electrical whine you mentioned is usually due to a shorted rectifier diode which is allowing AC current to pass through to the electrical system. A common way to blow diodes is to jump start another car or getting a jump start.

 

I replaced the Auto Tensioner, Serpentine Belt and Idler pully In April of this year hoping to resolve what I thought was a belt slipping noise. All 3 components were Gates brand parts from O'Reillys.

I guess it's possible it's something causing the alternator to give out but I didn't get a ton of confidence from the place that rebuilt it. They were recommended by a co-worker but both times I had it fixed I asked them what was wrong and they told me they just replaced everything.

Not sure what my next step would be at this point

 

im using a powermaster 200 amp alternator. been about 3 years ago now

 

I went down to Advance Auto parts and bought a new (Not Reman) ToughOne Alternator. After talking to the guys at PowerMaster I didn't think it necessary to buy a 200 AMP alternator. I installed the new alternator and the issue with the voltage dropping at 3500RPM's has been fixed. Of course nothing is without consequence as now the voltage gauge will randomly spike from 13 down to just above the red for about 2 seconds then go back to normal. Sometimes this will happen once on my 5 mile drive to work and sometimes it'll happen 3-4 times. After 3 days I have yet to find a discernible pattern. After 4 alternators I'm starting to think I've got a faulty ground or some other sort of electrical short. Any one with similar issues in the past have any suggestions on where to look or am I just unlucky enough to get 4 bad alternators?

 

Check the small connector with a single wire at the alternator. Make sure it has a steady 12v while the engine is running. You might have to run a special wire to allow you to check it while running.

Another possibility is a broken or loose braided copper strap from the frame rail, near the ABS unit, to the driver side engine block near the mount.