Whine in stereo and audio module fault

[Mike Langlois]

Greetings All,
My 2002 V70 has developed a loud whine when the radio is turned on. It is an after market radio that worked well for 3-4 months and suddenly the whine developed. When I power the radio from a battery (not the car) the whine disappears. Vida is showing a fault in the audio module; I am not sure if this is from the radio change or a real problem in the module. The small fan that pulls air across the thermistor (for climate control) seems to stay on at all times and I do have a "phantom" draw on the battery, that deplete is in about 2 weeks. I have a distinct feeling the that 'forever running fan' is involved somehow, since the whine is present with the car off and the car on. I would appreciate any thoughts on this. Getting ready to take it to a Volvo specialist if I can't figure out what is wrong.
Yours,
Mike