New Alternator Has Bad Brushes?

[badge49]

A few days ago I pulled my dead 95A alternator and replaced it with a "new" Duralast 130A alternator from Auto Zone. Today was the second time I've driven the rig since the install. The alternator hums like it has bad brushes...just like the old one. I can replace it under the warranty, but I'm open to advise or comments before I do. Here's a cell phone clip of the hum:
Turn on your speakers to hear it

 

[badge49]

Oh, I forgot to say that the clip was taken when the truck was warmed-up, idling in park, with no accessories on (no load).

 

[b33p3rmcg]

Sounds to me like a bad bearing? I have personally had experience with rebuilt alternators from Autozone. Took me 3 tries to get one that didn't have a bad bearing or a bent shaft. I won't buy them there anymore.

 

[BrooklynBay]

Did you check for vacuum leaks, and if the cap on the IAC didn't pop off? Bad brushes would cause a problem in the charging system. It would cause either a low charge or no charge condition with a battery light.

 

[badge49]

Did you check for vacuum leaks, and if the cap on the IAC didn't pop off? Bad brushes would cause a problem in the charging system. It would cause either a low charge or no charge condition with a battery light.

I do have a vacuum leak, but it is unrelated and pre-existing. The old alt. only charged at high RPM, so the truck ran mostly on the dual Optimas. Both have since been fully core charged at AZ, so the new alt. doesn't have much charging to do. Oddly, it didn't make any noise today despite being driven off road? Maybe it needed to be boken in again?

 

[Cobraguy]

Brushes won't cause a noise. If you saw how they work, you would know that's not going to happen. Bearings cause noises. And, little known...bad diodes can cause noises (humming) because they get the current running around inside the alternator like crazy

 

[badge49]

I've gone through three "new" Duralast alternators in the last day...needless to say, I'm tired of installing defective parts. The guys at AZ have gotten to know me well. Each of the alts. have hummed loudly, but tested OK for charging, at the store. Is there anything besides the alt. that could cause an alt. to hum? I'm going to try Kragen next since I've used every single alt. that AZ has in my town.

 

[Turdle]

dura blast alternators are junk-

 

[ezrider440]

hey there
this is absolutely the same issue i had with an alternator from autozone..............they are total garbage, in fact i tried to return it with the claim that the dam thing made terrible noise, granted i paid something like 200 for a new alternator , they didn't want to return it because the dummy put in their test machine and wasn't able to detect the noise....................long story short i went to a local store bought a rebuilt alternator for like 110, the rebuilt works terrific, meanwhile with the crap one, i opened it and cut the ends to regulator so i can get a return on my money............go local!!!! autozone is crap

 

[badge49]

Update

Since the weekend ended and I have to use my truck for work, I left installed the latest alt. that they gave me, even though it made the classic"hummmm" sound. I've been driving the truck daily about 40 miles and the hum has gone away!? I'm still thinking I might get rid of the Duralast since I don't want it to go back to being bad anytime soon. Any recomendations of brands in the $160 range?