W211 android head-unit static noise

[SL03WLY]

Hi

Recently fitted an android head unit, hooked itnup using most decoder so uses original agw amp. However when starting it up regardless of volume input there is static noise in the background. When turning car off i get a loud pop sound too.

Any ideas? Would I need to ground the headunit frame to the chassis or the the headunit toast ?

Thanks

 

[Ted]

My first thing would be to make sure the power feed is routed away from any harness, and add a ferrite core (or two) to the power cable

 

[ALFAitalia]

If that does not work...try disconnecting the negative from the back of the unit and temporarily wiring a new one as far away from the unit (say the boot) as possible. Often this will cure a feedback loop. Happened on my last one and after I put in a permanent new negative (connected near the rear wheel arch!) it was clear as a bell.

 

[SL03WLY]

Thank you both. Wil try that out.

 

[KennyN]

Had an issue with screen interference when i fitted an aftermarket reversing camera , solution was to use a "clean" power supply directly from the battery wired through a relay.



K

 

[SL03WLY]

So have ordered some Ferrite Core and a Ground Loop just in case it doesn't work.

Below is the back of the headunit. It uses a 20 pin molex (Lablled A) I believe for the RCA and It's ground too. So the ground from there is connected to the 12v socket's ground cable. I will take one of the screws off of the back and attach a wire to it and then the other end to the chassis somewhere.

Also noticed, this unit has a USB DVR and the tone does change when I unhook its connector and reconnect. So will add as many ferrite cores I guess.

The power cable on this is from the 40 pin Quadlock. But only 2 cables yellow and black. These attach to the power cable from the AGW. The MOST Fibre cable is taken off of this to be put into the MOST decoder box which is also where the 2 RCA cables attach to too.

 

[SL03WLY]

 

[SL03WLY]

 

[SL03WLY]

Hi,

So I tried the Ferrite Core/bead's today but no luck. Not sure where I am supposed to place them if I am honest.

I tried it on the power cable then the negative but no change in sound. Also tried it on the RCA cables, no luck. I also wrapped bare wire around the RCA's and then attached to the head unit also no change.

I've taken the loom out today and will remove all the cloth tape.

Any other suggestions? I still have to try the ground loop out.

Thanks

 

[Ted]

You should be able to loop the cable through the bead - possibly more than once.
Still worth a try if you have it all out.
Also make sure that the metal body (if there is one) is well earthed.
While it’s all out, you could disconnect the antenna to see if the interference is being picked up by the aerial or not.

 

[SL03WLY]

Cheers, will give that a crack.

Another thing I noticed was this didnt occur when I used their 6m cable which plugs the head unit directly into the speakers. now that I'm using the MOST decoder its causing this noise issue. Would having the MOST fibre running with the power cables (As it uses the existing harness to AGW) cause all this problem I am having? I'm thinking of adding another ground from the AGW to the chassis as well. I'm hoping its not the head unit as that will be a pain getting another one.

For RCA it utilises this cable:



This then connects to the MOST Decoder:

 

[Ted]

I can’t comment on the MOST ring as I’m not familiar with it, but I would be (very) surprised if fibre could interfere with analogue signals.
Might be worth checking that everything that should be grounded is well grounded locally to a good clean earth if that’s possible - making sure that any additional earths are kept away from any power cables.

 

[poormansporsche]

Had an issue with screen interference when i fitted an aftermarket reversing camera , solution was to use a "clean" power supply directly from the battery wired through a relay.



K

They get everywhere

 

[colinallcars]

Cheers, will give that a crack.

Another thing I noticed was this didnt occur when I used their 6m cable which plugs the head unit directly into the speakers. now that I'm using the MOST decoder its causing this noise issue. Would having the MOST fibre running with the power cables (As it uses the existing harness to AGW) cause all this problem I am having? I'm thinking of adding another ground from the AGW to the chassis as well. I'm hoping its not the head unit as that will be a pain getting another one.

For RCA it utilises this cable:

View attachment 139843

This then connects to the MOST Decoder:

View attachment 139844

Have you contacted Connects 2 for advice?

 

[SL03WLY]

So @Ted , I bought a 14 pack of ferrite beads and stuck them on everywhere there was a power line. Lo and Behold the alternator whine has gone. Thank you for that. I'm just left with this static noise which was further surpressed when I fitted a ground loop isolator. However when connecting the loops ground cables the alternator whine comes back. Bit werid. I attached a ground cable to the head unit case but that made no difference so.

 

[Ted]

I’m running out of options now
There’s s number of ways for the noise to get in - either via the power feed - mitigated by the ferrite beads, the ground(s) ensure that everything that should be grounded is well grounded, or induced into the wiring - try keeping it well away from al other cabling just to diagnose it.
Although it almost certainly isn’t coming in via the aerial circuit, just try disconnecting the aerial from the head unit - that will eliminate that. If it does, make sure the aerial is grounded at the aerial and into the head unit.
Also make sure that when testing, the car is how you would drive it - just having the bonnet up will allow electrical noise into the car.

 

[SL03WLY]

Its alright fella. Honestly getting rid of the alternator whine made a huge difference. Its just the static noise when I'm not listening to anything or on call.

I took apart the 20 pin cable for the RCA and seperated the 2 so they have their own ground as per pin diagram. I will probably do a bit more around here and there as the space is very tight where once fitted everything behind is being crushed. I've had to place the loop isolator and MOST decoder boxes on the side under the glove box (Velcro'd). I've bought some shielded RCA cables. See if that helps any way.

With the antenna I did connect it and ground it but it made no difference connected or not connected. It's probably going to be the head unit. I will try to add a ground cable to the amp and some ferrite cores there too to see if it helps.

But quick question, as I don't know but with the ferrite cores, can you run multiple cables through it or does it have to be only 1 wire (loops or not) per ferrite?

Also yes the install was done in the car with doors; bonnet closed.

 

[Ted]

Good question - I’ve only ever run one cable and I’m 90% sure you can’t run any more through a single core.
Back in the day you could also get a choke which might help, but I can’t help but think this might be more fundamental (head unit or cabling not well shielded for example.

 

[m80]

You might consider that the new HU is faulty, it looks Chinese and that wouldn't be a surprise.
Likely off on a tangent with this but USB kit 'often' creates RF interference. While the symptom is to reduce the FM signal, so only strong stations are heard, it 'may' be that any USB kit is back feeding into the HU.

But tbh I would want to eliminate a faulty Chinese HU as 1st step.

 

[SL03WLY]

So I took the advise given by another member on here and connected directly to the speakers, and voila no static or any other fancy sounds.