Okay, so, this is weird. I put in a Pioneer head unit, and connected the illumination lead up to the factory's brown illumination wire.

Now, if I put the brakes on, and put my blinker on, the head unit flashes when my lights are off. It's as if the thing is getting a signal to "dim" from the brown factory wire. Has anyone else had this problem? Seems to me if my car was wired incorrectly (a short), if I had the brakes on with the blinker, not only would my Pioneer unit try to dim, BUT, my parking lights should also come on! And they don't!

I'm thinking the reason is this: That brown wire is getting a bit of voltage when the brakes are on, and the blinker is on. But, it's not enough voltage to turn on a bulb. I bet the Pioneer unit "dims" when any voltage is present at the illumination wire. I'm thinking of adding a diode with a certain threshold voltage, so if the voltage on the factory "dim" (brown) wire isn't 12 volts, the head unit doesn't see any voltage. Isn't the IN1004 diode like this?

Sound good?

Just unhook the illumination wire. I have never hooked it up on any radio, and never poses a problem. The lights will be on constantly when your driving and you cant dim them, but some radio have a option where you can dim it manually.
~Tim

Tim, thanks for the suggestion, but this is the first radio I've had with an illumination circuit, and I'd like to keep it!

Any other ideas? Or will I just wind up trying the diode, and letting everyone know how it goes?

What does the illumination curcuit do anywayz? I wired my Xplod head unit to the one in my old S-10 and the only thing it did was turn my stereo on whenever I turned on my parking/driving lights, even if I had the keys in my pocket!! Great way to tell if my lights were left on, Better then that damn "BEEP BEEP BEEP BEEP" that it did. But when I disconnected it, nothing changed but that.

go directly to you parking light circuit, a good place is at the head light switch, forget color but check with volt meter. If the brown wire is the illumination for the stereo which I think it is then the is a problem with your wiring in your car. It is conected to brake lights instead of parking lights, it may only flash when one turn signal is on and maybe not the other.

That's what throws me off... wouldn't my regular parking lights flash, too? If the brown wire is getting power thru the brake lights, my whole rear taillights should be lighting up!

that brown wire has been spliced some where to the wrong wire,