Took a 2k mile trip recently and in the middle of trip a hissing, screeching noise was coming from the speakers and the radio was not even on. It only went away when the engine was shut off and back on again. Now whenever I turned the radio on the noise comes back and for it to go away the car has to be turned off and back on. Currently the fuse to the unit is removed. Does anyone have a clue what is the problem? Is this repairable or do I have to replace the entire head unit? If replacing is the only option what is the procedure involves besides disconnecting the battery? The unit is a HU-613 on a 2004 V70 2.5t.