Originally Posted by Gustav_H
I'm not sure if I follow you now Arnold_F.
Should I try to connect he RCA cable ground to the chassis ground of the car?
Otherwise I've found some fairly cheap products that seems to do the trick. They cost about 15 euros.
NOO!!!!
Connect mp3 to RCA.
But don't connect all the mp3 power line... just the +12V to mp3player (charger)
Don't connect ground to mp3 (charger)!