I have a zumo 665 navigation system installed on my 2012 ultra limited. The dealer installed it and it has a wire from it to the accessory port on the front of the radio. My question is when I have the radio set to accessory is the only way I can hear the navigation commands but I can't hear any music, just navigation. Any ideas would be appreciated. I thought I would be able to listen to music and the navigation commands would interrupt the music then music? Thanks