Speakers humming, High Charge from alternator...almost redlined (Page 1/1)
Forrest FEB 05, 06:52 AM
EDIT: Low gas was causing the buzzing. Thanks for the help guys.

Hi guys. I did a search for this but nothing came up.
1988 V6 112k miles.
With the stereo off the speakers are emitting a humming sound that is in sync with the RPMs....goes up and down in frequency.
Also the alternator is charging bigtime. Its right at the red line on the gauge. I thought maybe a low battery is causing it but I charged the battery up and same issue.
Any ideas?
Thanks in advance for your time.

[This message has been edited by Forrest (edited 02-05-2022).]

slicknick FEB 05, 10:26 AM
Sounds like bad diodes in the alternator. Shorted even. Not sure where you'd get the hum from other than AC ripple leaking past.
Patrick FEB 07, 03:16 AM

quote
Originally posted by Forrest:

EDIT: Low gas was causing the buzzing. Thanks for the help guys.



Sure... but it wasn't causing your alternator to overcharge.


quote
Originally posted by slicknick:

Sounds like bad diodes in the alternator. Shorted even.



I've had alternator diodes fail, and it seemed to me that the voltage was lower than it should've been, not in the red of the Voltmeter as the OP has reported. I'm no electronics expert, but wouldn't this be an indication of maybe a failed regulator?
Forrest FEB 07, 09:22 AM
I think you are right Pat. Ill look at testing it with a multimeter.
The 88 is my daily so I need it running.
If need be I will pull the regulator off my 86
Patrick FEB 07, 11:29 AM

quote
Originally posted by Forrest:

The 88 is my daily so I need it running.
If need be I will pull the regulator off my 86



My memory may be failing me... but isn't the regulator internal to the alternator?
olejoedad FEB 07, 12:00 PM
Yes, it is internal.
And the 88 and 86 alternators are different.
theogre FEB 07, 12:59 PM
88 has CS130 alt and Does Not use a "Diode Trio" like SI uses.
When Full Wave Rectifier is bad often won't cause dead battery or high volts. (This is partly why CS and related generate More energy for given power use from engine.)

Do not trust dash gauge. measure volts at battery or + box below C500.

Over Volt can be wiring problem or bad alt.
discon the Negative battery "post."
Check wires at alt for loose ends etc.
Should see 0Ω if you pull side plug and measure large red wire "pin" in the plug and alt output bolt. You test Wires w/ Ω meter. Not the alt for this.
See my Cave, Alternator Sense

if ok, have Alt bench test at most local parts store for free.

------------------
Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
(Jurassic Park)

The Ogre's Fiero Cave

Australian FEB 22, 01:43 AM
Alternator sucks as pain in ass to remove but i would pull it out and service it new pins springs brushes as could be at end of tether but good bearings and shaft.
Forrest FEB 22, 02:12 PM
Yeah nothing to worry about. As Ogre said the gauge was a little misleading. I put a multimeter to it and read ~14.7v which eventually went down to 13.5.
Speakers humming was just low gas. Several posts about it but slipped my mind. My gas gauge does not work so I go off mileage and seems last fill-up the trip meter got stuck.... I ALMOST ended up walking home. She just made it home....sadly it took me a few to figure out what happened. After pulling the fuel filter to make sure it wasn't packed with rust or something I had my son turn the car over and no fuel came out....outta gas.
My little wife had a good laugh at that one.