Questions about engine whine and ground loops

[JeffM 10+ year member]

I have a engine whine in my system so I would like to learn more about the issue so I can get rid of it. The noise that I have is only present when the engine is running. What would be some common causes of this? Also, what is a ground loop?

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[jco1385 5,000+ posts]

search much?

 

[dman4486 5,000+ posts]

read the sticky at the top of the electrical section

 

[JeffM 10+ year member]

I read that thread but it still didn't answer one of my questions. Are engine/alternator whines and ground loops only present when the engine is running?

 

[jco1385 5,000+ posts]

well, the alt and engine aren't doing anything while they are off. i'd say yes

 

[JeffM 10+ year member]

So how would a bad amp ground or RCA ground cause a noise when the car is on, but not when its off? If the there is a bad ground then wouldn't the noise be there regardless if the engine is on or off?

 

[jco1385 5,000+ posts]

maybe something (a part of your cars electronics) is causing the noise. are your amps close to any eec's or other electronics?

 

[dman4486 5,000+ posts]

So how would a bad amp ground or RCA ground cause a noise when the car is on, but not when its off? If the there is a bad ground then wouldn't the noise be there regardless if the engine is on or off?

read thatvvvvvvv

 

[helotaxi 5,000+ posts]

The noise that you hear is voltage ripple from the alt. The alt generates AC which is then rectified to DC by the alt's rectifier. Rectified AC is not perfect DC, there is a bit of a fluctuation in the voltage. The battery filters out a lot of the ripple but not all of it. When you have a bad ground (or a componenet in the system that has poor ground isolation of the signal path) the component partially grounds through the outer jacket of you signal cables. Since a lot of amps reference the signal to the outer RCA conductor, that voltage ripple in the ground now traveling on the outer RCA conductor is introduced into the amplified signal.

Improving your component grounds reduces the presence of the ripple in the signal path.