[raykay]

Each switch and corresponding seat are on separate circuits, each on their own 12v feed from the ignition switch, and their own Earth cable to the connector at the bottom of the centre console.
Orange/White is the 12v feed from the ignition switch, with a sealed joint in that cable to each seat for the temperature sensor and seat heaters.
Yellow is the return from them to the switch.
Black is the Earth connection to the switch.
When the switch is first operated, the Yellow is connected to Earth, the sensor will also be on and the seat heaters operate. When the sensor switches off, the 12v feed is lost, and the electronics in the switch, sensing the open circuit, switches off, and stays off - although the switch itself may still be in the 'on' position.