What to do if Adapter 3 can't boot up normally?

If you don't connect the cable of your Adapter 3 to the flight controller, and only power Adapter 3 with a battery, will the display show the correct battery voltage? 

Normally, if you connect Adapter 3 through the cable to a flight controller and plug in a battery to Adapter 3, it will show the battery voltage(marked as  ⑤ in the picture above) correctly. Also, the Bluetooth/WiFi status light(marked as  ① in the picture above) will blink to indicate the flight controller is detected.

But if you see the display can't show complete information for example the voltage numbers are not complete or even not shown up, or the display shows the boot-up process repeatedly, this might be caused by a high current draw of the USB output from the Adapter 3's cable.

Adapter 3 can output up to 1A through the USB cable at 5V. Usually, a flight controller itself consumes about 100mA or below. The current draw of the flight controller can be a little bit higher if the receiver is connected. But most of the time, the total current draw will be below 300mA.

There are 2 reasons to cause the flight controller draws too much current.

1. Hardware damage inside the flight controller.

2. Big current-consuming peripherals(usually a VTX) connected to the flight controller are powered up when the flight controller is applied power through the USB port. This is usually a hardware design mistake of the flight controller or a user error.

To solve this problem, please try to connect your Adapter 3 to your other flight controllers to see if the problem still exists. If yes, that means the problem comes from Adapter 3 itself. If no, that means you need to consider the 2 reasons mentioned above.