Audio Systems: Headunit, vw jetta wolfsburg, vw jetta

Question
2003 VW Jetta Wolfsburg 1.8T/55000mi.Headunit works ,but no sound in speakers.Also I can"t change chanels.I check all fuzes-OK,pull out headunit,check fuze on headunit-OK.All connection fine.What is the problem?  

Answer
What on earth could make you thing that the headunit works if you haven't connected it to an amplifier and speakers that you know are working? Furthermore, if you don't have another source to plug into your amplifier, how do you know that if that's working. If you don't have access to the equipment to use as testing or a scope & generator then I suggest you bring it to someone who does.