Audio Systems: Car Radio Turns on by Itself, vw new beetle, roof antenna

Question
Thanks Tom,

I really appreciate your help on this.  Yes, the radio does have sound when it comes on. I am afraid that technically much of this is over my head. In order to examine the possibles that you identified, is it necessary to remove the radio from the vehicle?  Is this something that a layman can do or should I turn it over to a professional.  I did take it into the dealer, but they found nothing.  I expect that their expertise is probably not much better than mine.  Their answer on a second visit would  likely be just to replace the unit.  Is there any way that battery connections could cause the problem or the connection to the roof antenna?  the CD player is in the trunk - should I check the connections there?  I did remove and examine the fuse which is ok.  Let me know if you have any additional thoughts.

Thanks,

Bill

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Followup To
Question -
VW New Beetle 1999. Radio/tape/CD player is original equipment. The Radio goes on by itself even when car is locked and no key in ignition. Also goes off when car is in operation, then comes back on. on-off-on-off. I come out to car in the morning and the radio is on - spooky stuff.  

Answer -
Hello Bill,
I have seen this problem a few times before. On one radio I found a leaky capacitor that shorted together several power traces on the circuit board. When the radio comes on with out the key in the ignition does the radio have sound playing also? I looked over my notes on this kind of problem and on another radio the electronic switch for Radio/CD operation had defective solder connection on it that would make the radio come on by itself. I will check into this problem deeper and come up with some other clues for you. If you need Tech Help in the future feel free to contact me direct at: tdeser@zoominternet.net

TOM,  T&D ELECTRONICS

Answer
Bill,
This Radio uses 2 power supply lines to it, one for station memory and the second for main power switched on with the key. You can try to measure the voltage on switched lead when the radio comes on by itself(with the ignition key off)
If you have voltage when the radio comes on with the key off then the problem may be that something is shorting in the car's electrical system that is sending power to the radio. Also You may want to ask the dealer to replace the radio to see if this corrects the problem. If you need Tech help in the future feel free to contact me direct at: tdeser@zoominternet.net

TOM, T&D ELECTRONICS