I'm pretty sure he said more than once in this thread that he has already run ground wires from the chassis to the stock ground point.

 

Post #27 (yesterday): "have not yet tried to ground the radio housing"

 

From post number one: "I know this can be a ground issue so I added a extra ground cable from the headunit to the same ground point the head unit already uses, made no difference."

 

Tried it this afternoon, no difference unfortunately.

I find it strange that even with rca or speaker connectors disconnected i het same sound.
also it is weird that when i turn on the lights the sounds (amp) shuts down.

i’ll try it with another head unit when i can.

any other thoughts that could cause my problems?

perhaps good to mention that there where no issues at all with the original radio...
only thing i noticed was that the original radio could me turned without key in ignition..

 

I was not clear on this one, i added a extra ground cable beside the existing one, not from the metal around the radio itself.

 

First you need to figure out why the amp turns off. Black-Orange should go to "System enable" (C0098). There should be a 12V DC signal coming out of the head unit enabling the amp and stay on as long as you want the head unit make sound. Do you have a multimeter?

 

I don't think there's much you can do about alternator whine/static through speakers. I had an Acura with this issue all OEM stock and never messed with. and tried to solve it but had no luck. It happens to most cars when you crank the volume up.

 

If there is whine or other noise, then it is just wrong wiring, a faulty unit or bad design. I have a non-stock unit and it is absolutely noise free.

 

I totally didn’t think about the radio i have in my other car, haha!
a pioneer avh-x8800bt.
i’ll try that radio in the disco tonight if i have the time and will let you know what happens.

 

I think the problem has been found!

I've connected my pioneer radio and everything works like it should;

With rca cables connected to the metra harness there is a very little hiss, you can barely hear it, if I put the volume on '1' its already gone.
When I turn on a consumer like the headlights the sound stays on.
When I turn the key to position 2, the sounds stays on.
When I start the engine, there is no engine whine and the sound stays on.

So my conclusion, all the cables of the vehicle are luckily OK, it's the headunit that's causing the problems.