Hello. My new to me 2007 V70 2.5T has developed an apparent issue with the factory radio which iirc is hu-805. Today the display is working but there is no sound. the unit seems to respond to all button presses except the on/off vol. ****. Also of interest is that when I shut the car off, the radio display dims but continues to show changing information. I can not seem to turn it off. Sorry if I'm posting a read the manual question, but I've had the car for 3 days and I did not get the owners manual. Thanks in advance.