Why does my mp3 only come out one side of my speakers in my car?

I have a JVC KD-R600 radio in my car and when I plug in my ipod or phone into the auxiliary port it only plays out of my right speakers. I read a lot of reviews saying this was a great radio and I paved a lot of money for it. I would hope its capable of playing out of all speakers. If anyone knows how to fix this please let me know.