Should the radio switched 12v wire grey connect to the constant?

The grey wire typically serves as a switched 12V power source for the radio, meaning it provides power only when the ignition is on. It should connect to a switched power source rather than a constant 12V source, which is always on. This ensures that the radio turns off when the vehicle is off, preventing battery drainage. Always refer to the specific wiring diagram for your vehicle to confirm proper connections.