Car Stereos: Car stereo died, jvc cd player, radio power

Question
I have a JVC cd player in my 1997 jetta that was installed when I got it in Sept 2008. It worked fine until about 3 months ago when I turned the key off the stereo stayed on. So for the last three months I have been using the off/on button for it. My girlfriend had taken it on a trip and locked the keys in the car. A tow guy unlocked it from the passenger side. Then all of the sudden the deck would not turn on to play CD's or radio. If you hit the display button it will light up and show time then go blank again. Also it will eject and load disks while lit up then immediately die again. I checked fuse in back of deck and it was good. Also I tried buying a used deck that worked fine but before I bought it I plugged it in and it had the same problems. It was a different model but same brand.Could it be a fuse under the dash or hood? I had a door dinger when the drivers side was open and it stopped working also when the door was unlocked by the tow guy on the passenger side. Any thoughts?


Answer
Hi Kurt,

It certainly sounds like a problem with the vehicle, not the head unit; but I'm not sure it's anything as simple as a fuse.  

Volkswagens are a bit unusual when it comes to radio power, compared to other types of vehicles.  They commonly use the "key sense" function for radio power, rather than controlling the radio through the key switch itself.  For example, most vehicles will turn the radio on when you switch the key to the accessory position, and turn it off again when you switch the key off.  The VW has a more complex circuit that activates the radio when you turn the key on, but keeps it working when you turn the key off until you remove the key from the ignition.

It sounds to me like you've been having problems with the key sense function in the key switch.  Originally, the key sense stayed "on" at all times, so that the radio stayed on even after you removed the key. Now, either the key sense function isn't working at all, so the vehicle isn't detecting the key in the ignition; or the circuit just isn't getting power.  Either condition might cause the problems with the radio and with the door chime.  A blown fuse is probably the first thing to look for (try looking for a fuse labeled with a key symbol) but it's also possible that there's a fault in your ignition switch.

The "memory" power wire behind the radio doesn't have a problem--a JVC head unit will load and eject CD's, as well as turn on the clock display, with just the memory wire powered.  For actual operation, though, you need to have power on the accessory power wire as well.  One possible solution would be to find an alternate power source for the accessory power wire--you might disconnect it from the radio harness, then extend it to the fuse box and tap it into a key-switched fuse such as the windshield wiper or power window fuse.  Alternately, you could just connect the accessory power wire to the memory power source (along with the memory wire) so that the radio stays on regardless of key position.  If you look at the wiring behind the head unit, the "memory" wire is yellow, and the "accessory" wire is red.

Hope this helps!

Brian