I have a 96 jetta GL. It's got an after-market pioneer 12-disk changer connected to a pioneer deck. The source button on the deck switches it back and forth from the disk changer to radio; however, I never listen to the radio, so I don't use the button. But, one day after work, I got in it and it was on the radio; and the source button wouldn't change it to the disk-changer (pist me off bad). it's not the source button itself and the disk changer is still getting power -so I'm assuming it's not a fuse.