Car Stereos: 2002 Chev Cavalier

Question
Im trying to wire up KD-J440 JVC deck, and im trying to wire
it into my 2002 chev cavalier. i cant get deck to turn on,
ive wired decks before and have not have had so much
trouble. can you tell me what im spose to do? I wire up all
8 speakers correctly. and the 2 big grounds, there is sitll
a small black wire, small purple wire, and gray wire left
over. Im hardwiring it of course because i cant afford a
connector. but there isnt a switched 12v+ line for my car,
where should i obtain this? Ive found a 12v+ orange wire in
my steering column wire harness that when probed with
multimeter gives me 12V with keys turned back or clicked
ahead, and 0V when key is out. Should i be wiring this to my
fuse box? Id love to know because this is my 2nd deck i
thought 1st was broken. please tell me this isnt a 2nd dud
deck. Thanks, regards. Shawn

Answer
Hi Shawn,

My guess is that your leftover black and gray wires are for illumination.  Chances are they aren't necessary for your new head unit; you'll need to insulate them so that they can't cause a short circuit.  Also, the violet wire should be insulated and left disconnected; this is a data wire, and if you let it ground out or connect it to anything, it could cause problems with lots of other vehicle systems.

Keep in mind that without the proper adapter, you'll lose the vehicle's warning chimes when the factory radio is removed.  

Usually, if I'm looking for a key-switched power source in these cars, I use the brown wire from the key switch harness.  This should be the true accessory wire, and isn't shared with the heater circuit like the brown wire.  If you tap this wire, make sure to put a 5-amp fuse on your new wire near the tap point.  Otherwise a short on  your new wire could damage the vehicle's ignition circuit.

You can test your deck by connecting the yellow and red power wires from the radio to the orange wire in the vehicle's radio harness.  This should allow you to switch on the new deck, independently of the key switch.  I wouldn't leave it permanently connected this way, because of the chance of draining your battery; but it will work for testing.

Hope this helps!

Brian