I drive a newer GM truck. The sensor that detects lights (GM vehicles typically put this on the far right side of the dash) either activate the running lights (ambers) or flip on the headlights when there isn't enough visible light hitting the sensor. This is much like one of those fancy night lights for kids that shuts off when you turn on the bedside lamp, but lights back up when you kill the lights at bedtime.
You have to have manual override ability on high priority systems like lights and doors. While you have a clicker to open your doors, you still have a key slot and inside toggles to lock and unlock the door.
Manual: You can't live without it.
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I like the switch so I can shut off the OEM light array and kick on the Daylighters.
