Low voltage with accessories - Change alternator?
Melting Slicks
Joined: Apr 2001
Posts: 2,030
Likes: 363
From: Lubbock Texas
The "whine" in car audio is due the AC ripple not filtered by the alternator entering the AC -speaker level or most often pre-amp 500mv level. Quite often due to different impedances between the radio and amplifier- and most of the time due to a lesser quality amp and or cheap unshielded RCA cables-
DC
Le Mans Master
Joined: May 2003
Posts: 8,872
Likes: 3,548
From: Fernandina Beach FL
2023 Restomod of the Year finalist
2020 C3 of the Year Winner - Modified
Chasing the whine can be frustrating. I used quality components and cables, installed them correctly and still got a slight whine. I put filters on both the 12V switched and 12V battery leads to the head unit which took care of most of the whine. I did get rid of the whine completely for awhile by installing a capacitor across the alternator based on a thread somewhere on this site. But, I couldn't keep the recommended capacitors from failing. It may have been a heat issue.
DC
DC
Like I said- the alternator IS the source of the whine-as the AC voltage- IIRC was around 100HZ at idle and changed (up in frequency) with RPM that is introduced in a DC system.
So you could filter it at the source by a cap or everything powered off the battery or have equipment that has isolation circuits to not let the AC in the pre-amp section.
My point still being- add all the grounds you want - it will not hurt anything NOR increase ( could possible decrease) alternator whine in the stereo system.
Richard
Melting Slicks
Joined: Apr 2001
Posts: 2,030
Likes: 363
From: Lubbock Texas
It is a Kenwood system on my '73. Amp is direct to battery as is the 12v battery lead to the head unit. But, the 12v ignition wire to the head unit comes from the fuse block. I suppose I could add a relay so as to have both 12v leads to the head unit being supplied directly from the battery. Hadn't thought about that before. Hmmm.
Do you have a recommendation for what type of capacitor I could put across the alternator that would filter out the whine and withstand the heat and vibration of the engine compartment?
DC
Le Mans Master
Joined: May 2003
Posts: 8,872
Likes: 3,548
From: Fernandina Beach FL
2023 Restomod of the Year finalist
2020 C3 of the Year Winner - Modified
Completely agree with you on the grounding. For ground loops to be an issue, there would have to be a potential difference between one or more grounding points. I went down this road with a fairly sophisticated Fluke meter and always got zero voltage between any two grounding points on my '73. My experience was adding the alternator to frame ground cut the whine down a bit but did not eliminate it.
It is a Kenwood system on my '73. Amp is direct to battery as is the 12v battery lead to the head unit. But, the 12v ignition wire to the head unit comes from the fuse block. I suppose I could add a relay so as to have both 12v leads to the head unit being supplied directly from the battery. Hadn't thought about that before. Hmmm.
Do you have a recommendation for what type of capacitor I could put across the alternator that would filter out the whine and withstand the heat and vibration of the engine compartment?
DC
It is a Kenwood system on my '73. Amp is direct to battery as is the 12v battery lead to the head unit. But, the 12v ignition wire to the head unit comes from the fuse block. I suppose I could add a relay so as to have both 12v leads to the head unit being supplied directly from the battery. Hadn't thought about that before. Hmmm.
Do you have a recommendation for what type of capacitor I could put across the alternator that would filter out the whine and withstand the heat and vibration of the engine compartment?
DC
The radio (Kenwood started this in the late 80's) uses the ignition wire to just trigger the radio on- that should not be a source of noise. If the constant power (yellow wire) is connected to the battery AND the ground- you might have a bad- or rather going bad alternator. Take your meter- turn on the headlights and see how much AC power is showing up at the battery- more than 500mV- diodes bad.
A top quality noise filter would be the "Newmar" ones out there- marine quality- just do a google search to find them.
Richard
Le Mans Master
Joined: May 2007
Posts: 5,007
Likes: 1,114
From: North tonawanda NY
In regard to the ground loop I just remember from installing stereo and amps many of the documentation as well as a book on car audio talking about having all the grounds branching from the same source vs different sources and area of the vehicle and how grounding at multiple pionts of the vehicle can introduce noise.. Heres something I found quickly while googling it.
https://www.lifewire.com/whining-noi...x-input-534592
And yes Ive found that moving the ground source on more than one vehicle had resolved or reduced the whine.
In this case adding the additional ground to the alternator likely helped reduce it because it eleminated any existing difference in ground potential.
https://www.lifewire.com/whining-noi...x-input-534592
And yes Ive found that moving the ground source on more than one vehicle had resolved or reduced the whine.
In this case adding the additional ground to the alternator likely helped reduce it because it eleminated any existing difference in ground potential.
Last edited by augiedoggy; Aug 17, 2019 at 01:19 AM.
Melting Slicks
Joined: Apr 2001
Posts: 2,030
Likes: 363
From: Lubbock Texas
In regard to the ground loop I just remember from installing stereo and amps many of the documentation as well as a book on car audio talking about having all the grounds branching from the same source vs different sources and area of the vehicle and how grounding at multiple pionts of the vehicle can introduce noise.. Heres something I found quickly while googling it.
https://www.lifewire.com/whining-noi...x-input-534592
And yes Ive found that moving the ground source on more than one vehicle had resolved or reduced the whine.
In this case adding the additional ground to the alternator likely helped reduce it because it eleminated any existing difference in ground potential.
https://www.lifewire.com/whining-noi...x-input-534592
And yes Ive found that moving the ground source on more than one vehicle had resolved or reduced the whine.
In this case adding the additional ground to the alternator likely helped reduce it because it eleminated any existing difference in ground potential.
You make good points as well. I'm reminded of helping a friend many years ago chase down a whine in his stereo system. Despite all of the ground connections being good, we finally eliminated the whine by connecting three grounding points together with wire. Guess his frame just wasn't up to the task of being an effective conductor.
Apologies to the OP for derailing your thread.
DC
Le Mans Master
Joined: May 2003
Posts: 8,872
Likes: 3,548
From: Fernandina Beach FL
2023 Restomod of the Year finalist
2020 C3 of the Year Winner - Modified
In regard to the ground loop I just remember from installing stereo and amps many of the documentation as well as a book on car audio talking about having all the grounds branching from the same source vs different sources and area of the vehicle and how grounding at multiple pionts of the vehicle can introduce noise.. Heres something I found quickly while googling it.
https://www.lifewire.com/whining-noi...x-input-534592
And yes Ive found that moving the ground source on more than one vehicle had resolved or reduced the whine.
In this case adding the additional ground to the alternator likely helped reduce it because it eliminated any existing difference in ground potential.
https://www.lifewire.com/whining-noi...x-input-534592
And yes Ive found that moving the ground source on more than one vehicle had resolved or reduced the whine.
In this case adding the additional ground to the alternator likely helped reduce it because it eliminated any existing difference in ground potential.
When you have the difference in potential ground - say a bad ground or not optimal one on the radio- since electricity is lazy (likes the least amount of resistance) it's going to travel down the audio ground (shield on the RCA cable)- that acts as an antenna - picks up noise.
Same with the antenna cable- the antenna is grounded at the back of the car- if that ground is better than the one at the radio- then the shield cable acts as an antenna and will pick up noise too.
The alternator is what is GENERATING the noise...adding another- better ground makes it work less- more efficiently - that's why the noise is lower/eliminated- has nothing to do with a ground loop.
.
Thread Starter
Burning Brakes
Joined: May 2017
Posts: 774
Likes: 375
From: Seattle WA
You make good points as well. I'm reminded of helping a friend many years ago chase down a whine in his stereo system. Despite all of the ground connections being good, we finally eliminated the whine by connecting three grounding points together with wire. Guess his frame just wasn't up to the task of being an effective conductor.
Apologies to the OP for derailing your thread.
DC
Apologies to the OP for derailing your thread.
DC
I learned what I needed to and gained a whole lot more information. I like it!
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Corvette ZR1X Will Be Pacing the Indy 500, And Could Probably Race, Too!
Verdad Gallardo
Top 10 Corvettes Coming to Mecum Indy 2026!
Brett Foote
Top 10 C9 Corvette MUST-HAVES to Fix These C8 Generation Flaws!
Michael S. Palmer
10 Revolutionary 'Corvette Firsts' Most People Don't Know
Joe Kucinski
5 Reasons to Upgrade to an LS6-Powered Corvette; 5 Reasons to Stay LT2
Michael S. Palmer
2027 Corvette vs The World: Every C8 vs Its Closest Competitor
Joe Kucinski
10 Most Common Corvette Problems of the Last 20 Years!
Joe Kucinski
5 MOST and 5 LEAST Popular Corvette Model Years in History!
Joe Kucinski
2027 Corvette Buyer's Guide: Everything You Need to Know!
Joe Kucinski
Le Mans Master
Joined: May 2006
Posts: 9,993
Likes: 1,136
From: League City Tx
Scott, switch over to a CS144 alternator and don't look back...(if you are running factory/repro brackets).
I got my High Output CS144 from www.alternatorparts.com about 10 years ago and it still charges great. A 140 amp alternator with good idle amperage is pretty much a MUST today when running fans, fuel pumps, FI etc....
If you are running a serpentine or other front runner type system, you'll have to find an alternator that works with that bracket system.
I have a thread here on CF tech from when I installed the CS144 alternator with pics, info, tips etc... It'll show you how you need to mod the "C" bracket etc.
I got my High Output CS144 from www.alternatorparts.com about 10 years ago and it still charges great. A 140 amp alternator with good idle amperage is pretty much a MUST today when running fans, fuel pumps, FI etc....
If you are running a serpentine or other front runner type system, you'll have to find an alternator that works with that bracket system.
I have a thread here on CF tech from when I installed the CS144 alternator with pics, info, tips etc... It'll show you how you need to mod the "C" bracket etc.