When something goes amiss with your Kingsong 14D, such as the lights no longer working, the wheel no longer self-balancing, or simply not powering up, the most common culprit is the control board.
As the brains of the wheel, containing the firmware that controls speed and lighting, to the gyro that manages the self balancing motor action, without it working in tip top shape your wheel will not work as designed.
Thankfully, replacing the control board on most electric unicycles is something you can tackle with some simple hand tools and a guide like this.
Watch this video to learn how to replace the control board on your Kingsong 14D. Video by eWheels.com