Alternator whine issue

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JustinStone

aspiring nutrient
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Florida
I've isolated my alternator whine to two components: RCA's or Headunit. After ensuring a good ground on the amp, unplugging RCA's at the amp, and relocating the HU ground to a metal behind the radio I'm still getting pretty obnoxious whine.
Here's some things I've noticed:
- gets higher in pitch with rpm
- gets quieter when volume is 0
- very quiet when radio is off
- almost inaudible when in "standby" source
- only noticed the whine after installing rockford 600.4
- when using 3.5mm jack, tone can change pitch based on where the cable is sitting in the car with no phone attached
- whine is present on all sources except standby
- the whine gets intensely loud when charging phone and using aux (ground loop whine??)
- when charger and aux are in, the loudness of the whine increases with headunit volume
- probably unrelated, but my alternator does produce a high pitched sound itself from the bay, the whine inside the car sounds very similar in pitch.

any ideas on how to either fix it completely, or at least knock it down from making my tweeters play 5 watts all the dang time

thank you
 
Last edited:
I've isolated my alternator whine to two components: RCA's or Headunit. After ensuring a good ground on the amp, unplugging RCA's at the amp, and relocating the HU ground to a metal behind the radio I'm still getting pretty obnoxious whine.
Here's some things I've noticed:
- gets higher in pitch with rpm
- gets quieter when volume is 0
- very quiet when radio is off
- almost inaudible when in "standby" source
- only noticed the whine after installing rockford 600.4
- when using 3.5mm jack, tone can change pitch based on where the cable is sitting in the car with no phone attached
- whine is present on all sources except standby
- the whine gets intensely loud when charging phone and using aux (ground loop whine??)
- when charger and aux are in, the loudness of the whine increases with headunit volume
- probably unrelated, but my alternator does produce a high pitched sound itself from the bay, the whine inside the car sounds very similar in pitch.

any ideas on how to either fix it completely, or at least knock it down from making my tweeters play 5 watts all the dang time

thank you


Is your power wire running along or crossing over the rcas at any point?
You could try a noise filter. Sometimes they help
 

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Is your power wire running along or crossing over the rcas at any point?
You could try a noise filter. Sometimes they help
I have my RCA's ran in the center console and my power wires run along the driver's rocker

also I replaced my ignition coil today and the sound is a little quieter??
 
I have my RCA's ran in the center console and my power wires run along the driver's rocker

also I replaced my ignition coil today and the sound is a little quieter??
I'd get a pair of jumper cables and start grounding things out while the engine is running and the speakers are whining and see if it stops. Poke around the engine bay grounding the body to frame/ frame to block etc. If one particular ground fixes the problem connect a permanent wire there.
 
meh, some $10 cables. I'm putting money aside for sundown 4chnl RCA's; shielded and ofc. After bolting a block ground to the battery the sound got quieter but I still notice it from time to time.

Get shielded RCA's and see if that helps. When electricity moves through the fabric of space time, it creates an electromagnetic field. So, if you have unshielded RCA's (it's like a faraday cage), then what can happen is your RCA's pick up random EM fields in your car or around the RCA wires, and the RCA's get energized by those other random fields, and that's how you get noise introduced into your amp, sometimes.
 
99.9% of the time this is caused by a ground loop. You may have the battery grounded to the frame, the headunit grounded to the dash and the amp grounded to the body. I'm not saying that is the exact case but that's what causes a ground loop. What you want to do is connect all of these grounds. That doesn't mean they have to all have the exact same grounding location but running an extra ground wire to the body usually solves the problem. Sometimes even a grounding strap from the body to frame can fix the problem. There are also head units that have grounding issues. You didn't mention what car, what head unit, or anything. Soo.....
 
Where exactly did you ground it to
Battery, at most 6ft
You didn't mention what car, what head unit, or anything. Soo.....
pt cruiser
headunit is kenwood kmmbt525hd; grounded on the same bolt as the battery's chassis ground, and ran with 12awg ofc to headunit's wires.
amplifier is rockford 600x4; 0/1 ofc ran to battery posts with d4s 6spot-distro, and 4awg copper reducer at amp
front battery is xs d1200, 2 months old
all chassis connections stripped to bare metal
 
Get shielded RCA's and see if that helps. When electricity moves through the fabric of space time, it creates an electromagnetic field. So, if you have unshielded RCA's (it's like a faraday cage), then what can happen is your RCA's pick up random EM fields in your car or around the RCA wires, and the RCA's get energized by those other random fields, and that's how you get noise introduced into your amp, sometimes.
I do have the extra wire bundled underneath the radio as well... just seen it... lmao
 
OK
Get the shielded RCA's for sure but if you have a 6 foot ground wire running back to the battery that might be your issue.
Ground wire should be ideally 18-36" long. The shorter the better.
Do you own a multi meter?
If not invest in one.
Set it to continuity, it should beep when the two prongs are touched together.
Tape a wire, single speaker wire will do (long enough to get from your battery to where your amp is mounted) to the neg terminal on your battery and the other end to one of the prongs on the multi meter
Now use the other lead from the meter to poke at existing bolts that are within a couple feet of where you want to mount the amp
When it starts beeping you have found your ground
FYI- The location I mount my amps in is based on where the best ground is located so if you have to move your location do it

Question, if the amp is only 6 feet away from the battery, where is it mounted?
Under one of the seats?
 
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