When the ignition of the vehicle is turned off, the remote turn on wire stops transferring voltage and the amplifier turns off. If the remote turn on wire is connected to a wire in the vehicle that has constant voltage, the amplifier will always be on.

Where is the remote wire on a car stereo?

The turn-on wire (also called the remote wire) is located behind the stereo. On aftermarket stereos, its usually a blue and white wire. The remote wire will tell your amplifier to turn on whenever the stereo is powered up (usually, whenever the vehicle is turned on).