I have a strange issue with my 04 beetle. I get a strange whistling / whining sound that only happens when the radio is on, but it doesn't come from the speakers. It slightly modulates in pitch and volume, seemingly in sync with acceleration. Any ideas?
More common if the car has a Monsoon audio system.
I had this problem with my 2003 with a Monsoon system, dealer had worked on the car and the wiring connection between the battery and the fuse box on top of the battery. The smaller wire that connects to the positive battery terminal was loose after a dealer repair on my car.
Most likely alternator whine. Petty normal under some conditions.
First check battery terminals and the smaller wiring connected to the terminals. Check the fusebox on top of the battery, make sure everything is tight.
These will be the most common problem areas. The wiring on the back of the alternator could also be loose, however, this is less likely. Additionally the alternator could have a failed diode or internal problem as well.
Lastly there could be some other grounding problem in the car or at some of the radio/Amp modules.
A quick test would be to use a jumper cable to connect the engine to the negative battery terminal and see if there is any change to the whine noise.
I have the same problem, sort of, in my 2008 convertible.
We have a Sirius car unit hooked up to our radio as well. The VW dealer installed it in 2011 when we bought the car. It has worked with no problems at all until recently when my wife was in the car and it got rear ended. Ever since then, there is the whine only when the satellite is on. FM, CD etc sound great. It's just when the satellite is on? I tried switching the satellite unit but it still did it. Any thoughts? Must be a connection somewhere?