on wich of these 4 wires? and what is it going to do technically?

 

You can do it on any one of the rca lines that is going to the 4 channel amp that you have. It is going to provide a proper ground path that you do not have right now due to the fuse being blown. It should get rid of the alternator noise if the unit is not damaged beyond all hope.

 

So i better ground my 4 rca wires on my unit chassis?

 

Yes, This is what I should have done on my old Alpine 9885. It seems you are having the same issues.

 

You only need to do it to one rca cable, not all.

 

ok so I'll connect a wire on the bolt that holds my unit in the factory bracker, split this wire in 4, disconnect my rcas and wrap the wires on these, replug the rcas. I'm right?

 

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and what about this? does this work?
also can my blown fuse reduce the quality of my sound?

 

On my old setup I could take out the red RCA from the amp and it worked, what was the red one for? I thought it was left/right.

 

No, no no no no no no. Do not pass go, do not split any wire in 4. Nowhere did I say to split a wire in 4.

 

Do not unplug the rca's and wrap a wire around either. Nowhere did I say to unplug the rca's and do that either.