Stereo ignition power is run off the stock location for switched power. I used the existing connector. Constant voltage is supplied from a wire that I am not sure where it originates but it is a constant +12.
Not sure of the answer here but my point was,
If the stereo is wired so that it goes off when you turn off the car, then the ignition switch could be the problem.
If the stereo is wired so that it stays on when you turn the car off and the stereo power went off when this happened, then it's not the ignition switch.