Help with engine whine

[Mrbojangles]

I'm in a dreaded ground loop alternator whine noise problem. It's too loud to ignore.

I've had this same system in two previous cars and the noise has never been this loud.

I have 4 gauge power wire from battery to a fuse all the way back to a block that splits to one 400w amp for the subs and a 1000w 4 channel powering 4 speakers. I also have the HU powering two door speakers.

When the key is only on accessory, there is no noise. Sounds great. If the key is "on" but engine not running there is noise. When the engine is running there is more noise that matches the rpm of the engine.

I've grounded the two amps close to bare metal about 2 feet away, sanded down with a nice new bolt. If I unplug the 1000w, the noise is barely noticeable so the sub amp is fine as is. The two speakers run by the HU alone also no noise so I know it's from the 1000w amp.

I've tried multiple RCA cables with no change at all. I ran a ground wire from the 1000w to the stereo chassis and the noise dropped only very slightly almost unnoticeable.

I've read all kinds of things but can't seem to get past this one. Was hoping for some advice before I tuck my tail in and bring it to an audio shop.

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[Mayhem]

I had a bit of engine whine when I started my build with my most recent car.

I just add chassis grounds until it goes away.

I actually ended up adding two grounds to my front battery and two extra on top of my four to my rear bank. Between all my batteries I have about 10 grounds.

Zero noise as of right now.

 

[Mike Waters 10+ year member]

Definitely a ground issue. Keep trying different ground spots.

 

[Mrbojangles]

Thanks for the info. Wasn't sure if too many grounds would cause more loops or other problems.

When you say adding grounds to the front battery, do you mean running a ground wire from the amp to the negative terminal or from the terminal to the frame?

 

[Mayhem]

Terminal to the frame.

Don't even waste your wire doing a ground run from your front battery to the rear.

The grounds on your amp(s) are most likely fine.

There are probably a couple stock grounding points your battery is already using.

Just adding another run to the existing ground can make a big difference.

 

[Mrbojangles]

Another round of testing.

Ran wire from neg terminal on battery to a ground point on frame. No difference.

Ran RCA cables outside the car, no difference.

Removed the ground shield from a test RCA cable, no difference. (Someone told me that's what a ground loop isolator does).

Maybe run the power wire on the other side?

 

[Mayhem]

Another round of testing.Ran wire from neg terminal on battery to a ground point on frame. No difference.

Ran RCA cables outside the car, no difference.

Removed the ground shield from a test RCA cable, no difference. (Someone told me that's what a ground loop isolator does).

Maybe run the power wire on the other side?

Maybe try grounding your RCAs

Grab a bit of speaker wire and have the wire wrapped around the RCAs on your HU. The other end can be grounded to a screw on your HU.

It's kinda a bit rednecky but it actually works.

 

[tymoto21 10+ year member]

^x2

I bet it's a pioneer radio

 

[Mrbojangles]

Haha yes, pioneer. It's an oldie but well, hey it works.

But holy ****, Mayhem. Grounded the RCA cable and noise is completely gone along with a headache.

I can't thank you enough, if you were close buy I'd buy you a couple beers ??

 

[LosIsATool 5,000+ posts]

Haha yes, pioneer. It's an oldie but well, hey it works.But holy ****, Mayhem. Grounded the RCA cable and noise is completely gone along with a headache.

I can't thank you enough, if you were close buy I'd buy you a couple beers ??

You popped the pico fuse by hot swapping the RCAs. It's common.