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Alternator Question / Whistling Noise


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8 replies to this topic

#1 samneric

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Posted 24 November 2009 - 07:18 PM

Hey all,

Been a while since posting since my 85 Brat's been mostly behaving... one or two issues have finally popped up though... firstly... Alternator.

The symptoms as they occured...

Replaced alt with recon B/A.

Everything fine..... few months later I get a whistling noise when the engine revs (sounded cool at first - like a turbo :) )... Figured it can't be belts cause they are new... Figured alt was playing up.... couldn't afford new one so left it.

Next thing... (this has happened before).. the volt gauge starts revving in time with engine rpms.... Still couldn't afford to change alt so left it.... Finally got another recon alt today. 55 amp premium from Napa.

When switching it in, there is a capacitor shaped object on the back of the old alt that has a wire going to the alt terminal. I thaught that was a voltage regulator? so I always swapped it on to replacement alts. It has several burn holes in it so I didn't swap it across this time...

Installed new alt and started car. Still get the annoying whistling sound but the volt gauge stays level and doesn't rise with engine rpms....

So questions are.... Is that capacitor looking object a voltage regulator? Is it needed? Is there a voltage regulator built into replacement 55amp alts???? What could be causing the annoying whistle?? Could it really be a bad belt and if so, why would a new belt do this so soon????

Sorry for all the questions but I guess I was saving them all up since my last post on the forum....

Any help appreciated! I am certainly willing to take a photo of said object or answer any other questions....

..Oh Yes... I also disconnected a rather large music amp incase that was overloading the alt and damaging it...

Steve

Edited by samneric, 24 November 2009 - 07:25 PM.


#2 ihscout54

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Posted 24 November 2009 - 09:33 PM

So questions are.... Is that capacitor looking object a voltage regulator?

Its a "filter" its purpose is to eliminate alternator noise/disturbances that might interfere with sensitive electronics in your car.

Is it needed?

Without it; you will get a whine but only through your speakers. I would get a replacement for it.

Is there a voltage regulator built into replacement 55amp alts????

Yes as long as it is the correct unit for your car.

What could be causing the annoying whistle??

As long as your sure its not coming through your speakers from the lack of a suppressor, then it could be a bad pulley (if applicable) bearing, water pump, or any rotating divice under the hood. You need to isolate where this noise is coming from.

Could it really be a bad belt and if so, why would a new belt do this so soon???

Perhapse if it is contaminated or improperly tensioned.

#3 samneric

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Posted 25 November 2009 - 08:27 AM

Its a "filter" its purpose is to eliminate alternator noise/disturbances that might interfere with sensitive electronics in your car.

Ok cheers - I will look on the web for a replacement filter.

As long as your sure its not coming through your speakers from the lack of a suppressor, then it could be a bad pulley (if applicable) bearing, water pump, or any rotating divice under the hood. You need to isolate where this noise is coming from. Perhapse if it is contaminated or improperly tensioned.

The noise is definately coming from the engine and it doesn't sound like a slipping belt. I've always heard belt noises as a high pitched squeal that is there even on idle. My noise comes in just after accelerating.

I will look into the pulleys. The alt belt is fully adjusted to its maximum tension and there does seem to be a little slack - I can turn the pulley - admittedly only a bit - by hand with the belt at its tightest....

Maybe the belt is too big...

As I remember, I replaced the water pump when I changed my head gaskets...

Steve

#4 Cougar

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Posted 25 November 2009 - 04:22 PM

The voltage regulator is built into the alternator and the "filter" is a capacitor. It bypasses unwanted high frequencies coming from the alternator into the power lead to ground.

The squeal is most likely due to a bad bearing in the idler-tension pulley.

#5 samneric

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Posted 25 November 2009 - 05:34 PM

The voltage regulator is built into the alternator and the "filter" is a capacitor. It bypasses unwanted high frequencies coming from the alternator into the power lead to ground.

The squeal is most likely due to a bad bearing in the idler-tension pulley.


Bad bearing - makes sense! the sound is coming from that area - I can test that by removing the a/c belt.... I guess you can buy the bearing or do you need a new pulley???

Where do I buy the capacitor????

Steve

#6 Cougar

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Posted 25 November 2009 - 09:21 PM

You can replace the bearing and I have done that myself. I would think a capacitor simlair that would be used for a set of ignition points would work fine. Something like a .1 microfarad@ 200volts should do the job also.

#7 ihscout54

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Posted 25 November 2009 - 10:50 PM

I would just go to the junk yard and find the capacitor. As for the pulley, it unbolts easily and the bearing can be removed. I matched it up at Lowes for like $5. On may car there were 2 of them.

#8 samneric

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Posted 29 November 2009 - 05:40 PM

I would just go to the junk yard and find the capacitor. As for the pulley, it unbolts easily and the bearing can be removed. I matched it up at Lowes for like $5. On may car there were 2 of them.


Yipee - it was the tensioner bearing - I could rock the pully back and forth with the belt on :)

And the rough idle/stalling that occured after taking off the air filter??? A vacuum leak caused by not reconnecting a pipe - that's what you get for not working on yer car for over a year :grin:

#9 Cougar

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Posted 30 November 2009 - 01:33 AM

Thanks for the feedback on this.




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