iPod video not working with car stereo, another exact same one does.. help!

[braz]

I have a 30gb version 1.3 iPod video, and so does my dad. I have an alpine CDA-9883 car stereo with an ipod cable hookup. For some reason his plugs into my ipod cable (not auxilary, an actual ipod hookup) just fine and works while mine only shows the song name and timer on the cd player but does not play any sound... is there setting I need to change or something? I already tried restoring it but it didn't help. PLEASE HELP! I need this to work in my car! thank you