source url Could be a number of things, but we don’t have enough info to give you an informed answer.
http://syaden.net/?giniefr=site-rencontre-france-gratuit&25b=02 Stock system? Aftermarket? What head unit?
Is an external amp powering the speakers or are they running directly off the head unit?
http://thenovello.com/alfondie/elkos/1312 If it’s stock — maybe the radio is not working correctly.
http://www.tangotec.com/?sitere=le-opzione-one-touch-che-probabilit%C3%A0-hanno-vincita&299=c3 If there’s an amp, you head unit may non-fading pre-amp outputs.