Alternator whine
Thread Starter
Drifting
Joined: Jul 2006
Posts: 1,483
Likes: 3
From: Newark, New Jersey
Alternator whine
Just when I thought the car was running fine and worked out all the gremlins, I develop a whining sound through the speakers. Looked through my FSM, and it sounds like alternator whine. It says to install a 250 MFD 100V capacitor on the alternator output lead. Problem is I cant find this capacitor. My local Radio Shack is useless. Has anyone experienced this and installed some sort of capacitor?
Thread Starter
Drifting
Joined: Jul 2006
Posts: 1,483
Likes: 3
From: Newark, New Jersey
Thanks Paul. I replaced the alternator less than a year ago. Its charging fine, about 14.3v at cold start up, then around 13.8. Should I still have it checked on a scope? The noise isnt always there. I just came back from a 3 hour road trip and the whine would come and go during different intervals. It also whines when the cassette is playing instead of the radio.
Team Owner
Joined: Mar 2001
Posts: 54,124
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From: Cincinnati, Oh USA
Normally the ripple on the d.c. output from the alternator is so small that it doesn't get into the audio circuits in your radio because the radio uses filter capacitors on the 12v line. As radios age these capacitors have their capacity reduce. I find 7 listings for electronic components for Newark, NJ on Google where you should be able to buy the capacitor. It won't hurt to buy a larger capacitance or a larger voltage rated capacitor. If installing the capacitor doesn't stop the whine, then you either have really bad ripple due to one or more defective rectifiers in your alternator, or the whine is from the audio amplifiers in your vette and they can be repaired by yourself by replacing the electrolytic capacitors on the circuit board of the offending amplifiers. The whine frequency will vary directly as the engine rpm if it is ripple from the alternator.
Thread Starter
Drifting
Joined: Jul 2006
Posts: 1,483
Likes: 3
From: Newark, New Jersey
Just checked the alternator on a scope and it checked good. Also checked the grounds which were tight. Goint to try looking for a capacitor to install and see how that goes.
Thread Starter
Drifting
Joined: Jul 2006
Posts: 1,483
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From: Newark, New Jersey
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Instructor
Joined: Aug 2009
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From: Broadway Virginia
Yes I repaired all four amps. As you may already know, the capacitors that Bose installed were faulty and prone to an early failure. They bought a bad batch of them from the manufacturer.
If I remember correctly, I did have the whine through the speakers even when the radio was off. This was due to .......and I am sure someone will correct me if i am wrong,.........the fact that the speaker [amps are] powered by a relay behind the glove box which is switched on all the time with the ignition, even when the radio is off. I believe they designed it so that the amps were already on, warmed up and ready to go when you turn the radio on.
If I remember correctly, I did have the whine through the speakers even when the radio was off. This was due to .......and I am sure someone will correct me if i am wrong,.........the fact that the speaker [amps are] powered by a relay behind the glove box which is switched on all the time with the ignition, even when the radio is off. I believe they designed it so that the amps were already on, warmed up and ready to go when you turn the radio on.
Last edited by walter schweigert; Sep 10, 2010 at 11:02 PM. Reason: [corrected subject verb agreement]
Thread Starter
Drifting
Joined: Jul 2006
Posts: 1,483
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From: Newark, New Jersey
Thanks Walter.
My problem comes and goes. I'll be driving and everything is fine. Then all of a sudden the whine occurs. Changing in pitch with the engine RPMs.This is with the radio on. If I shut the radio off, there is no whine. It sounds as if the whine is coming from all 4 speakers.
My problem comes and goes. I'll be driving and everything is fine. Then all of a sudden the whine occurs. Changing in pitch with the engine RPMs.This is with the radio on. If I shut the radio off, there is no whine. It sounds as if the whine is coming from all 4 speakers.
Instructor
Joined: Aug 2009
Posts: 146
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From: Broadway Virginia
In addition to the whine, I also experienced gradually worsening popping, and what sounded like a 'marbles in a meat grinder' sound when the capacitors totally failed.
Once the repair was done, both the whine and other noises were gone.
But, it initially started with the whine.
Once the repair was done, both the whine and other noises were gone.
But, it initially started with the whine.
Team Owner
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St. Jude '03 thru '24
You mentioned that the noise was only noticeable when playing the radio, not the tape deck?
Is it possible that a bad or "dirty" ground is the culprit?
Might try checking the antenna connections and grounds.
Is it possible that a bad or "dirty" ground is the culprit?
Might try checking the antenna connections and grounds.
