Installed an ipod adapter in my 09 ultra , installation went fine

problem im having is one time you turn it on and it works perfectly , the next time it shows up on the radio fine but no sound , turn it on and off a few times and it works , once its on it works perfectly , never cuts out etc

Im using my old iphone4 as a player and it charges and comes one and off as its suppose to

Not sure where to look , phone or cable or adapter when its working its fantastic

Thanks for any ideas

Dave