[Wall96cobra]

It's possible they hooked the ground wire of the cd player to the illumination wire, when you check the illumination wire with a voltage meter it will read like a ground (when the light switch is off) but when you turn the light switch on it sends 12v from the switch so someone could have mistaken that wire for a ground. But it could also be that the illumination wire is not hooked up to the radio and just laying in the dash behind the radio where it's probably touching metal and shorting out. I would just take the radio out and check for bare wires first.