Alternator whine fix?

[Radio Guy]

On older vehicles with metal dashes (during my car stereo installer days) it was very difficult to float or not ground a particular component due to all the exposed metal surfaces. Today its much easier to isolate components with mostly plastic interiors, but the ground loop isolator is still a standard item in most car stereo installs these days. Even if you isolate the components from ground and run a dedicated ground wire to a common point you can still have alternator whine creep in. Just get a ground loop isolator for your interconnect cables and enjoy a more simple install.

Sounds like why the guys I dealt with when buying equipment always advocating taking components to the same ground point - don't ground one thing at the dash and another under the hood and another in the rear of the vehicle. They said ground to the same point, a common ground. I recall them advising me years ago "avoid ground loops"

"Bad alternator" - typically diode (weak, bad) or stator issues.
All can be fixed.
When an alternator is fully loaded like I do on my test stand you can sometimes hear the problem in an audible whine coming from the alternator itself.
On these you'd probably know if there was an alternator issue - they would likely have trouble keeping up with full loads. Watch for abnormally low voltages.

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[red/green hawk]

Alternator whine is usually caused by one of two things, a bad alternator or ground loop. The way alternator noise propagates in a ground loop situation is the amplifier and another component of the stereo system are at a different ground potential and the RCA or low level audio cable shields between the components are trying to equalize the potential and current is flowing on them, inducing any and all noise in the battery/charging system into the low level audio cables.

The easiest way to fix this is with a capacitor type ground lifter or isolation transformer in the low level audio cables, which breaks the DC current path. Here is a cheap fix, never used this brand but it should work. https://www.amazon.com/InstallGear-Ground-Isolator-Noise-Filter/dp/B077Y5DLBB/ref=sr_1_1_sspa?crid=11ZCLQA0HHSZC&dchild=1&keywords=rca+ground+loop+isolator&qid=1628455091&sprefix=rca+ground+,aps,201&sr=8-1-spons&psc=1&spLa=ZW5jcnlwdGVkUXVhbGlmaWVyPUEyMVY3QVBPTkVXTkQ2JmVuY3J5cHRlZElkPUEwODkyMDUxMkY1RVA5NkQwT0M2JmVuY3J5cHRlZEFkSWQ9QTAyODkzMzMxUEJONU0xTFYwQzQyJndpZGdldE5hbWU9c3BfYXRmJmFjdGlvbj1jbGlja1JlZGlyZWN0JmRvTm90TG9nQ2xpY2s9dHJ1ZQ==

This one may be better quality and I have not personally tried this brand. https://www.amazon.com/XtremPro-Hi-...a+ground+loop+isolator&qid=1628455437&sr=8-13

I just ordered a 4 channel isolator off of ebay. I'll let ya know how it works after I get it.

 

[red/green hawk]

Ground loop isolator didn't help. Temp, easy fix. I went into the programming of the amp and the master volume was cranked. I turned it down a little and now the whine isn't very noticeable. Still there but negligible. I'm gonna leave it until I find an better routing of power and grounds.

 

[Radio Guy]

Some amplifiers are more prone to noise (ripple) riding on the power system and partially due to the amount of internal DC filtering inside the amp. An external high current noise filter may help but I don't want to recommend buying one without running some tests first. If you were local to me I have lots of DC noise filters I could loan out including one with a huge 40amp choke and about 5 Farads of capacitance that will actually run the amplifier for some time after you disconnect it from the battery.

You might borrow or steal a large capacitor, at least 50,000uf and place it across the power leads right at the amplifier. That will make a huge difference in most setups if the amplifier is sensitive to power line ripple from the alternator. A choke input filter with lots of capacitance is better and if a test with a capacitor improves things at least you will know what direction you need to go.

Ground loop isolator didn't help. Temp, easy fix. I went into the programming of the amp and the master volume was cranked. I turned it down a little and now the whine isn't very noticeable. Still there but negligible. I'm gonna leave it until I find an better routing of power and grounds.

 

[red/green hawk]

Well boys I want to thank everyone for brainstorming and giving me ideas and directions to go. I originally only disconnected the RCAs from the amp and hooked up the ground loop isolator. I trouble shot and determined it wasn't the RCA that were picking up noise. So I disconnected RCAs from the head unit preamp outputs and hooked up the ground loop isolator to those and presto no more alternator whine. I believe the preamp out puts are not good quality. Again thank you all for your help and expertise.

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