Help with isolating interference

[kamold]

Hi all,
I installed an aftermarket Chinese nav unit in my wife's MkV golf.
I have a noise problem that I'm not sure how to fix as I have no skillz

When the speakers are not muted there is a slight hiss from the door mounted stock tweeters. This is to be expected from a cheap amp and it's totally within my acceptable range.
However when the headlights are set to either auto or on, there is a buzzing noise of interference from the tweeters.

How would I go about isolating this noise? If I mute the speakers the buzz stops.

I have pulled the headunit out and checked for any bad ground connections. I have disconnected all the accessories like USB, GPS antenna, ipod, rear view camera etc.

Its isolated further to the radio antenna. With that unplugged the buzzing stops. I have a dual fakra to single motorola connector, but the same thing happened with the single fakra adapter that came with the head unit. Seems like the antenna is not grounded properly.

I tried running a bit of cable from the outer shield of the antenna connector to a spare ground connector on the head unit, which comes from the car wiring harness ground but it only makes a slight, but noticable difference. Maybe I need just different cable to ground??

Any suggestions welcome.

Thanks

[ian]

Hi does it make the noise when the engine is turned off,if it doesn't it could be coming from the alternator and might need a suppressor.

[kamold]

Nah it's perfectly quiet either on mute or if the headlights are off. (well there is a very slight hiss but nothing like the buzz).

I'll check all my connections again and try both shielding and grounding the antenna outer. Has to be something to do with the conversion of the oem diversity antenna to the aftermarket motorola connection..

[kamold]

Think I fixed it.

I isolated the ground for the antenna adapter by wrapping it in electrical tape and then pulled a new separate ground to the ground wire from the car wiring harness.

So looks like that ground is not properly isolated. No more buzzing!

Wow almost sounds like I know what I'm talking about

[Idle]

If you're only getting it when the headlights are on, then it's more than likely in the light circuit — bad contact, bad earth, switch fault, bulb failing, intermittent short — could be one or more of many possibilities.

That it stops when the antenna is disconnected suggests that whatever is playing up might be broadcasting the interference — but it's still controllable via the light switch, so should be downstream from wherever the light circuit fuse picks up its feed.

[kamold]

My googling for this issue found that it seems to be pretty widespread with similar units. People have tried all sort of things with varying degrees of success. Lots of info over on golfmkv.com.
Support from the seller in China was responsive, but fairly futile. The language barrier I think was a major hurdle. He seemed to either totally misunderstand what I was trying to tell him, or he provided limited solutions like

'good day

dear friend ,you need connact the brown wires and inseet the radio slot .pls have try

Attach the pictures ,pls check'

So overall I would say not for the feight of heart or those looking for an easy plug and play solution however I like tinkering and learning new things like this so didn't phase me too much. Just need to get it soldered up including the rear view camera so I can give my wife her car back.

[Transporter]

Try removing the fuses to isolate the circuit.

[kamold]

All good now. Have soldered up the temporary connections I made and put the head unit back in and no buzzing with the lights on or off