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Alternator whine and starting car with alternator disconnected

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Alternator whine and starting car with alternator disconnected

Old 09-15-2018, 10:59 PM
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Alternator whine and starting car with alternator disconnected

This is actually with my 2012 Accord V6 but I have it on good word that it's pretty similar to my 2008 TL

Annoying whine that is driving me crazy. Car is still under extended warranty and so far they replaced the a/c compressor/clutch and the power steering pump. Still the same and I since replaced the serpentine belt (Continental Elite 4060840) with same result. It's much worse when the a/c compressor is running. I've thought for awhile it is the alternator and told the dealership this and they said they checked the alternator and it's fine. We pulled a 2010 Accord V6 off the used car lot and it was far quieter with that noise being barely audible, so quiet that if you weren't looking for it you'd never notice it. One thing I have noticed is occasionally when the car is started it might not make the noise for a minute or two and then it starts. The whine is similar to this but not nearly as bad:



so can I start the car with the plug pulled off the alternator? I'd assume this would answer whether that's making the whine or not. I'm assuming doing what the guy does in the video (pulling the plug while the car is running) is not a good idea.

Thanks!

ETA: skip to 25 seconds in the video...

Last edited by Cheval; 09-15-2018 at 11:04 PM.
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Old 09-15-2018, 11:11 PM
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I bet it is your alternator
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Old 09-16-2018, 09:40 AM
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Originally Posted by Cheval View Post
This is actually with my 2012 Accord V6 but I have it on good word that it's pretty similar to my 2008 TL

Annoying whine that is driving me crazy. Car is still under extended warranty and so far they replaced the a/c compressor/clutch and the power steering pump. Still the same and I since replaced the serpentine belt (Continental Elite 4060840) with same result. It's much worse when the a/c compressor is running. I've thought for awhile it is the alternator and told the dealership this and they said they checked the alternator and it's fine. We pulled a 2010 Accord V6 off the used car lot and it was far quieter with that noise being barely audible, so quiet that if you weren't looking for it you'd never notice it. One thing I have noticed is occasionally when the car is started it might not make the noise for a minute or two and then it starts. The whine is similar to this but not nearly as bad:

https://youtu.be/hmPUUVwIJUU?t=25s


so can I start the car with the plug pulled off the alternator? I'd assume this would answer whether that's making the whine or not. I'm assuming doing what the guy does in the video (pulling the plug while the car is running) is not a good idea.

Thanks!

ETA: skip to 25 seconds in the video...
1st off, do not disconnect anything on the alternator or battery while the vehicle is started. You will damage other electrical components on the car. Does the sounds increase when you step on the throttle and stay with you when driving down the road? If so, there is a very good chance itís the alternator.( One of the diodes could be going bad that is giving you the sound you are hearing) You can always go to any Autozone or Advance Auto and they can check the volts coming out of the alternator. When the vehicle is running you should be at 13.5 to 14.5 volts. Must honda vehicles run around 14.1 to 14.4 If the volts are fluctuating a lot, it could be an alternator that is about to fail in the very near future.
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Old 09-17-2018, 12:48 AM
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Originally Posted by mcmanut View Post


1st off, do not disconnect anything on the alternator or battery while the vehicle is started. You will damage other electrical components on the car. Does the sounds increase when you step on the throttle and stay with you when driving down the road? If so, there is a very good chance it’s the alternator.( One of the diodes and/or bearings could be going bad that is giving you the sound you’re hearing) You can always go to any Autozone or Advance Auto and they can check the volts coming out of the alternator. When the vehicle is running you should be at 13.5 to 14.5 volts. Most honda vehicles run around 14.1 to 14.4 If the volts are fluctuating a lot( 10.0 to 14.0 volts), it could be an alternator that is about to fail in the very near future.

It's been doing this for about 2 years. I honestly think it's just an annoyance (along the lines of coil whine on a computer power supply or graphics card) more than something getting ready to fail but in the end who knows I guess. No it doesn't really seem to do it when driving down the road....it may be doing it but the road noise etc masks it? dunno... It seems to mainly be when the car is at idle (worse with the a/c compressing running) regardless if it's in gear or not. Give it the slightest bit of gas and the whine goes up and then down with the RPMs. Same just slightly turn the wheel and the RPMs go up and so does the whine then settles back down. Like I said it's like that video but that is like a 10 and mine is a 1. It's quite loud compared to that 2010 Accord (same generation 8g 2008-2012) we pulled off the lot. Nothing electrically seems to be wrong with the car. FWIW my 2008 TL doesn't even make the slight noise the 2010 Accord did...it's totally 100% silent with this noise. zip zero zilch.

I just figured I'd take my battery tender off my TL and put it on the Accord and let the battery fully charge with as much as it'll take, start the car and confirm it's making the noise, turn off the car and pull the alternator plug and start the car and see if it's making the whine. I think that would answer the question. I just wanted to get confirmation before I try that to make sure it's safe to do that. Don't want to fry the car. I couldn't really find much about this on the internet--everything seems to be people asking about disconnecting the battery while the car is running. I didn't know people would have to ask if that's safe or not...

Last edited by thoiboi; 09-18-2018 at 11:20 AM.
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Old 09-18-2018, 04:47 AM
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take off the accessory belt and see if the noise is present. If not it's one of the accessories such as the power steering, ac or alternator or it could be the idler and tensioner needing replacement.

OR

it's with the timing belt and you'll hear it even if you remove the accessory belt. perhaps a failed bearing in the timing belt tensioner or idler
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Old 09-18-2018, 11:09 AM
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I had a similar noise in my Accord, it was the tensioners. Replaced them, no noise.
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Old 10-12-2018, 12:07 AM
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Well, I finally got time to try this so I pulled the plug on the alternator and started the car and the result..........the same thing. zero change in the whine. so....up next is the tensioner like the above commenter mentioned. Anyone have any idea how to test the tensioner ? I thought about taking the one off my TL and putting it on (since everything is silent on that car) but the part numbers are different

2008 TL - 31170-RCA-A04
2012 Accord V6 - 31170-RV0-A01

so guess that's out. Anyone have any ideas? Seems the cheapest I see the OEM part is $250+

The car is still under warranty till end of December so I'd rather not spend $ on it but in order for them to do a warranty repair I have to prove to them that it is making the noise. hmm
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Old 10-12-2018, 12:35 PM
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I'm sorry but can someone clarify why pulling the alternator plug would test anything? The belt is still running the alternator pulley so it'd still be spinning.. Try removing your belt next
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Old 10-12-2018, 12:51 PM
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Originally Posted by thoiboi View Post
I'm sorry but can someone clarify why pulling the alternator plug would test anything? The belt is still running the alternator pulley so it'd still be spinning.. Try removing your belt next
It would remove the electrical load the alternator is currently supplying. If it were an electrical component like a diode, it might help. If it was a bearing, then it doesn't seem like it would make a difference.
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Old 10-15-2018, 12:34 AM
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Originally Posted by losiglow View Post
It would remove the electrical load the alternator is currently supplying. If it were an electrical component like a diode, it might help. If it was a bearing, then it doesn't seem like it would make a difference.

Ahh okay.. yeah, in my mind, it was a bearing so I was scratching my head trying to understand what that would accomplish.


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Old 10-17-2018, 11:51 PM
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