I bought 2 copies of this sensor bar, and both had the same problem, not really annoying but you must know:
The ON / OFF switch is reversed! Indeed, ON, the sensor bar does not work, OFF, it lights up!
My advice: connect the sensor bar on the console cable and allow the switch to OFF (which is actually ... ON), the console will handle light the sensor bar when it is needed and you will So never touch the ON / OFF button.
Works interchangeably on Wii and Wii U.
In short, a product of very good quality if you forget the reversal of the switch to the 2 models received.