# loose ground in wiring harness ? NOISE



## captainobvious (Mar 11, 2006)

SO I have been troubleshooting 3 different issues (found the culprit of one of them) and believe I may have found the problem for the second.

My car has 2 noise issues currently after getting everything wired up. I have noise (scratching static sound that is random in intensity but always there, and I also get some clicking and background hiss). This noise is present whether the car is started or not. The noise does not increase in volume when adjusting the source volume.

Noise issue 2: When the car IS started, I have the noise above, but I also have ground loop noise which is the standard alt whine/engine rpm dependent noise. 

While troubleshooting the noise(s), I found that touching/wiggling the ground wire in the source units harness caused the scratching noise. It appears to be a loose connection in the harness. Any way to fix that?

As for noise issue 2 (ground loop), I'm hoping the fix for the harness will help, but I also ordered up a DC-DC power supply which will isolate the audio ground in an attempt to fix it.


Thanks


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## ZMan2k2 (Mar 11, 2014)

As for the noise in the harness, I would say, find a nice piece of metal in the dash, and use a self-tapping screw, and make your own ground for the harness. I know in my truck, the dash bar is right behind the radio, so it would be easy for me, but I don't know about Mazda's and how easy it may or may not be. As for the ground loop, I would try to get a good ground for the HU first, and see if it cures problem two.


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## DBlevel (Oct 6, 2006)

I did end up running a ground from the radio to the back and grounded them to the same point as the amps which helped with the turn on/off pop. Helped to eliminate all the extra noise but still couldn't get rid of all the alt whine which I hope the pico issue will hopefully correct that problem.


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## captainobvious (Mar 11, 2006)

ZMan2k2 said:


> As for the noise in the harness, I would say, find a nice piece of metal in the dash, and use a self-tapping screw, and make your own ground for the harness. I know in my truck, the dash bar is right behind the radio, so it would be easy for me, but I don't know about Mazda's and how easy it may or may not be. As for the ground loop, I would try to get a good ground for the HU first, and see if it cures problem two.


When I say harness, I mean the head unit harness. The only thing I pick up from the factory harness is the accessory lead. I have a direct +12v run from the HU harness to the battery and a direct ground run from the HU harness to the chassis in the cabin grounded to the metal frame rail. The sketchy ground is that actual wire coming out of the HU harness. It's loose and wiggling it causes lots of scratchy noise.


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## captainobvious (Mar 11, 2006)

DBlevel said:


> I did end up running a ground from the radio to the back and grounded them to the same point as the amps which helped with the turn on/off pop. Helped to eliminate all the extra noise but still couldn't get rid of all the alt whine which I hope the pico issue will hopefully correct that problem.



I tried the same with the previous setup in this car to no avail. Although I had *far *less noise then, and I simply reduced amp gain to lower noise floor and didn't have much of an issue.


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## ZMan2k2 (Mar 11, 2014)

Can you use a pin to release the ground wire from the HU harness, and re-crimping it, then re-installing it. Other option would be to try and get a new harness from the manufacturer.


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## jode1967 (Nov 7, 2012)

running power and ground from the rear of my car is my next step in fighting noise. I think I have something in an idle circuit that is causing mine. when I first start the car the noise is the worst. once its ran for about 10seconds it drops in volume and then after another 8 seconds or so, it almost dissapears. I can hear the engine doing something each time it changes. and its very consistant on the times. Still have a bit of noise after all that, but it tolerable for me
hope yours is easier than mine has been


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## qwertydude (Dec 22, 2008)

You can eliminate alternator whine with judicious grounding. When I used to work as an avionics tech grounding was insane. With enough grounding you can eliminate the noise.

First ground your head unit ground directly to sheet metal. Never use the harness ground as it has connections which can increase resistance and cause ground loops. Then ground the head unit chassis to ground. If you've got unbalanced "normal" RCA's ground the negative to the chassis which should also be grounded.

Then comes cables. Make metal shielded twisted pair RCA's. The twisted pair carries the signal and the shielding gets grounded on both ends to the head unit chassis and amplifier chassis, although ideally it should be directly to sheet metal, with as little of the wire exposed as possible.

Then on the amplifier side again run as short a ground as possible and then also ground the chassis to sheet metal and also ground the RCA negative if they're unbalanced RCA's.

It's quite an extreme grounding case but I've never had it fail, when people say they've tried everything to get rid of alternator noise or ground loops, I ask them if they built their signal paths to FAA specs, inevitably they didn't and when they did, voila noise absolutely gone.


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## ZMan2k2 (Mar 11, 2014)

Wow! That's some great info. I've never gone to that length to ground anything in my stereo, but I can see it working well. A lot of effort, but that's definitely one way to go, and probably the best. Rep for you good sir.


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## captainobvious (Mar 11, 2006)

qwertydude said:


> You can eliminate alternator whine with judicious grounding. When I used to work as an avionics tech grounding was insane. With enough grounding you can eliminate the noise.
> 
> First ground your head unit ground directly to sheet metal. Never use the harness ground as it has connections which can increase resistance and cause ground loops. Then ground the head unit chassis to ground. If you've got unbalanced "normal" RCA's ground the negative to the chassis which should also be grounded.
> 
> ...



I thought in the auto environment you were supposed to keep the audio and chassis grounds separate?


Is this the layout you are describing? (see attached photo)

Thanks


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## qwertydude (Dec 22, 2008)

It depends, most unbalanced RCA's which is the majority of car stereos either have a grounded RCA or 200 ohm resistor to ground. But specifically with Pioneer head units the RCA negative is directly connected to ground but has a fuse which often burns out opening the ground path and introducing noise. The solution people employ is as simple as grounding the RCA negative.

The only time you don't want to ground the RCA negative is if you know you're using balanced inputs. Then if you're getting noise the twisted pair cable with shielding is best and grounding the shielding still helps a lot.


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## SPLEclipse (Aug 17, 2012)

Ground a piece of wire, play system, touch it to the chassis of the headunit. See what happens. You probably have multiple chassis grounds inside the headunit so that should complete the circuit. If it works make the ground permanent and eff the harness.

Of course, it _could_ be a loose 12v+ as well.


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## carter1010 (Sep 20, 2009)

I had a bunch of wines noises and pops. Turned out I had a .2 voltage drop across my power and ground. Might do a quick power and ground check. Got me to my problem right away after days of searching for what I did wrong and only took about 10 mins to check all my connections.


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## captainobvious (Mar 11, 2006)

I already installed a dedicated 12v dc-dc power supply which supplies an isolated ground and power source for the head unit. I took the ground from it direct to the chassis/case of the P99RS (and not to the ground wire in the harness). The scratchiness stopped (because I wasnt using the loose wire) but I still have some noise/alt whine so the quest continues...


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## captainobvious (Mar 11, 2006)

carter1010 said:


> I had a bunch of wines noises and pops. Turned out I had a .2 voltage drop across my power and ground. Might do a quick power and ground check. Got me to my problem right away after days of searching for what I did wrong and only took about 10 mins to check all my connections.



How did you measure this? Do you mean you were seeing 13v (for example) at the battery but 12.8 at your source input? What did you determine was the problem?


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## captainobvious (Mar 11, 2006)

Well, had a few minutes yesterday and did some more troubleshooting. I took the P99RS apart and removed the poly fuse to check if it was bad. It measured 0.2-0.3 ohms. I put a short piece of wire in place to test it without the component. Same alternator whine and noise. I also tried moving the source ground from the frame rail to the engine bay and same noise.

Next step is to try grounding all of the audio equipment to the same ground point to see if that makes any difference. Ill also pick up some ground loop isolators to see if they have any effect.


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## captainobvious (Mar 11, 2006)

Well, I figured I should update.

This is why troubleshooting can be so frustrating. You almost never have a problem like this so it's not one of the things you're even thinking about on the list of items to check...
There were two issues- first the RCA wiring harness coming out of the P99 was scored across a couple of wires and second- the power wiring harness had a loose ground connection. I ordered new harnesses direct from Pioneer and tested on my bench this weekend. The P99 is dead quiet now with no noise and sounds even better than I remember.  Even my wife was surprised when I hooked it up to my studio monitors and tested through a Diamond Audio amp. It was impressive.

That said, I already began purchasing items to move to a fully digital setup as I want to integrate an iPad with a wireless storage device to have access to my full library 

Thanks !


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## bigbubba (Mar 23, 2011)

I am having some of the same issues with noise and hiss in my setup. I have a P99 as well and have not thought about cheking the harness from the radio. Will have to check it out this weekend.


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## captainobvious (Mar 11, 2006)

It's definitely a much less common culprit with system noise so make sure you troubleshoot the usuals as well (ground location, ground loops, tight connections, etc).

Good luck!


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