Help - White Noise/Interference When Headlights are on!

[Randeep]

Hi All,

Can someone help at all...I have just had a new audio install finished which consists of a brand new Kenwood DNX521DAB (which is pretty cool), sub and amp, and second amp to power the door speakers. Power cable has been run on the left side of the car, RCA's and speaker cables are run on the right (driver side)

Everything is running fine, except when I turn on my headlights I get a very annoying interference sound. It only comes on when the lights are turned on regardless if the car engine is running or not It is not alternator whine, I already get a bit of that when the car is turned on. I have checked all RCA connections, headunit connections and checked that the amps are grounded correctly. I got my fitter to ground the headunit and RCA cables as well hoping this would fix the issue but no joy. Just to add, if I touch the brake peddle the volume of the noise decreases but not completely, you can still hear it.

Has anyone come across this before? I have a feeling it has something to with the grounding but as its to do with the lights I just dont know where to start!

Any help appreciated!

Thanks
Randeep

[SI-R32]

Only thing I can think off is as the RCA and speaker cables run down drivers side, they must pass the cecm to get to your stereo, all the lights find there way back to this box, so you may be picking it up there.

[Randeep]

I thought getting rid of alternator wining was going to be a pain!

I have been trying to search on the net as well, but cant find anything similar, there are a couple of cases with people having similar issues on chinese head units etc. Suggests this is not a common thing but I dont know where to start to get diagnosing!

[skard]

Try get a ground loop isolator for your RCA plugs, about a fiver on ebay.

Helped me when I had camera wiring next to amp wires.

[Andy]

Had this on mine;so ran the power cables down the passenger side-the power rca down the middle  and the speaker wire down the drivers side- mine still had a little wine with the lights on but not very loud ....  

[Squeeguk]

First thing is to double check all your earth points. You could have a ground loop somewhere. 9 times out of 10, noise is introduced into the system by bad grounding and not running wires next to each other. That can create noise, but not nearly as much as bad earthing.

With your issues with alternator noise too, I would go ahead and double check all your earth points, making sure they are as short as possible and as clean as possible and secure. Start with the battery and check your battery earth strap, then work your way back through the system. Earthing to the body correctly is better than earthing to the battery negative terminal.

Using a ground loop isolator is not the answer. It's like taking medicine to make you feel better temporarily, but not curing the root cause.

[Randeep]

Thanks for advice guys I was thinking of getting a ground loop isolator but I would rather try and get to the root if possible for cleaner sound. I hear ground loop isolaters can have an an affect of the clarity of the sound. Im not a pro at this kind of stuff can do bits but always worried I'm going to break something lol  

So earthing...both amps have a earth each relatively short, just long enough to put the seats down, they are screwed into the boot floor under the carpet as close as possible to the edge, the area was sanded down first. The head unit is already grounded through the iso, but added another wire running behind the glove box and screwed it into the side of the car near the passenger side.

Just find it strange thats it related to the lights only. I'm a bit of a noob looking at the engine bay of a Mk5 (its my new toy). I Will have a look at it tomorrow at some point now. Where is the battery earth strap end? Are there any points to defo check at all, ie known points that cause issues?

Thanks
Randeep

[Randeep]

Ok, so I checked the battery earthing and everything looks pretty clean. Had a look at some of the other points that I could visibly see and get too and gave them a quick clean but still no joy.

[skard]

Just to be clear as my last post probablt wasn't, I suggested a ground loop isolator for testing to determine whether it cuts down on interference (before you start undoing the work) rather than as a fix.

When I used one it cut out the interference I had, so pointed me towards a poor video cable for the camera thus I invested in a big fat insulated one without further issue, and subsequent removal of the isolator.

[Squeeguk]

Try reducing the length of the earth wire for your HU. It's not really necessary to actually run one of those at all unless you are running power direct from the battery to the HU. Try run it without that earth wire and see what happens. If you feel you must run that, then shorten the wire considerably and attach it to a point on the metal dash frame near the radio.

[sjefkuh]

good evening.. I know this is a very old post, but I came across this and this is exactly the same problem that I have with my car.. I am looking like crazy for the solution.. I have also tried everything that It was told here... but I went one step further... I cleaned every ground point that the car has that I came across and reconnected it... and I bought new headlights and light switch. and replaced the alternator and the brake light switch and tried the big 3.. and ground point from front to back.. added extra ground to the alternator, added extra ground to the brake pump.... laid the cables in and under the top along the outside of the car. etc etc.. I removed the radio from the wiring harness of the car.. so I installed the cables myself, already tried 8 different RCA cables, different types of speaker cable, even a plastic edge around the speakers where they come into contact with the door and even secured with tai rips to prevent them from hitting iron haha ​​and various radios and amplifiers etc etc.. replaced all the lights in the car up to the dashboard, I have no LED no xeon so I just can't figure it out anymore.. but like It has already been said here that as soon as you change the brake pressure, the noise sometimes disappears completely... so to make a long story short, someone here has already solved this problem...