Alternator Whine, Not Bearing? 2AZ-FE Engine

I have a 5th generation Camry with about 192k miles on it. 2AZ-FE engine. I hear a whine sound when pressing on the accelerator. It’s the original alternator. I hear this sound even with the car parked and pressing on the accelerator. I used a mechanic’s stethoscope, and it appears to be coming from the alternator. With the belt off, I spun the alternator pulley and it was quite.

It appears that this alternator only has a single bearing on the inside of the bearing. Is there something else inside of the alternator that could result in a loud whine sound besides the bearing, and if so what?

Looking online, it appears that the diode stack can short out resulting in a whine? Not sure how to test if this is the case or if the diode stack is a serviceable part?

My charging system seems to be working fine. With the car fine, I get slightly over 14 V at the battery. No battery light on the dash.

Any ideas?

If an auto electric shop can see it, they may be able to diagnose and fix it. Usually you have to bring the part into them.

Did you check all the pulleys? Did you run the engine briefly with the belt off and listen for the sound?

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When you removed the belt, it took the side load off the bearing’

So the bearing can still be bad.



what is battery voltage with key off? it’s possible that the alternator is working hard to keep a weak battery charged and cause a whine (which could still point to a weak alternator bearing.)

I was thinking of taking it to a shop, but with what they would charge I could replace the whole alternator by myself plus some.

I have not tried running it with the belt off yet. Kind of hesitant to even though I shouldn’t be.

I did try all the pulleys except for the power steering one, kind of large to turn by hand. I should have tried harder. With the stethoscope though, pretty sure it’s the alternator.

Thanks, any videos of replacing the bearing on this alternator I could use as a reference? Looking at the diagram it don’t look to hard.

Haven’t tried battery voltage with key off. I can see what that gives me.

From what you’ve said I’d replace the alternator (as long as you’re sure it’s not an idler pulley), assuming you’re up to it. Get a quality one.

Hey thanks. I don’t know if it’s normal on this car or not. But back when I had incandescent head lights I would notice they would dim when using the seat motor to move the seat up and down. Don’t know if this is the sign of the alternator failing or not being properly sized and I should get one that outputs more current? Was like that several years ago, but then when I switched to LED no issue with it dimming. I find it hard to believe they picked to small of an alternator, and maybe it has been going bad for some time. Just now noticed the whine sound though.

Debating if I should try and just replace the bearing or the whole thing. Maybe should get the bearing and a new alternator from parts store. If I can replace the bearing, just return the alternator. Not sure how difficult it will be to replace only the bearing, doesn’t look to difficult. Can’t seem to find a video of someone replacing it though. Want to make sure I got all the tools before trying to replace just the bearing.

If you’re going to tear the alternator apart to replace the bearing, might as well replace the the brush holder assembly too.


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Have you rebuilt other alternators? I’d rather have a pro do it.

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If you can R&R it yourself, you might be pleased with the work an auto electric shop can do at a reasonable cost.

Between buying your own parts, the time you spend (after all your time is worth something) removing, disassembling, replacing parts, reassembling, reinstalling, the real cost may just be about even with just getting a rebuilt alternator. The biggest determining factor is, and only you can say, what is your time worth to you? Just a thought.

While there’s only one bearing shown in the diagram, there must be a bushing in the rear casting, one that I don’t see offered on Rockauto.

if you tear into the alternator and replace one bearing, who says something else isn’t going to fail on it in a week or two on this alternator with 192,000 miles on it? You’ll be back to tearing it all apart with no warranty. Personally, I’d just buy a quality rebuilt with a year or two warranty and sleep better at night.


One idea, replace with new or rebuilt alternator but don’t turn in current one for core charge. Instead repair current one at your leisure, then you’ll have another alternator ready to go. If car is used by someone who needs reliable transport or else could face dangerous situation if car stops working, suggest to purchase replacement alternator from dealership.

Before I’d replace the alternator, and no noise hand spinning, and no in-out or twisting-force bearing play, I’d run the engine without it to make sure the noise I’m hearing is coming from the alternator. What sort of stetho-scope did you use? A length of hose, no contact, or the contact type?

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Brushes can cause a whine too. I used to overhaul my own but the last one was riveted and soldered to make it not easy to get apart. I just replaced one pre-emptively at 150k. Suggest just ordering a new one.

I have replaced many whining Toyota alternators, none of them had a failing bearing. The noise is from the shorted armature or rectifier bridge.


It is a touch based mechanic’s stethoscope.

I did buy a new alternator SDK. Like the idea of buying a new one and rebuilding the old one in free time.

Here’s the new one. Is the noise I’m hearing normal for this? Maybe I’m just expecting silent operation, when I shouldn’t be? The old one seems to be worse then the new one.

The '96 Lexus ES300 I had whined from the alternator from day one, I asked about it at my first maintenance, ‘they all do that’. Did the alternator used to be quiet on yours?

Thanks for the reply. Mine was a lot quieter until recently. The strange thing is, when I rotate the old one by hand with the belt off (it’s still on the car) it is nearly silent. However with the car on and pressing the accelerator down it is a loud whine.

New one makes sound whole rotating by hand. Got it from rock auto as a “new” part. It looks newish. Noticed some gunk or dirt in the right angle parts of the case, but looking inside the holes of the case, the internals have no rust and look brand new. I think it’s a new part, maybe they just cleaned up the casing and recycled it not sure to sell as a new part, but everything else looks brand new.

I’m guessing what happens in that case is the alternating current (higher than normal b/c of short circuit) causes something inside the alternator to vibrate b/c of changing magnetic polarity, maybe the core the copper windings go around, or the windings them self, mechanically oscillate and make a noise. Capacitor can make a whining noise as well, caused by forces produced in alternating electric fields.