If you own a WiiU, you might also own an external hard drive to go with it since the system’s internal memory is sorely lacking. This article exists to help those suffering from external hard drive woes, as they can be quite frightening.
The most important fact is that the WiiU does not generate enough power to power an External HD that is charged via USB UNLESS you use a USB Y-Splitter. The way it works is that an External HD that charges via USB must be plugged into the female port of the USB splitter, and then the USB splitter’s two male ends go into the WiiU. (I’ve plugged mine into the vertical USB ports on the back.)
If your external HD is receiving enough power, it should make a whirring noise when the Wii U is turned on and the HD is plugged in. (If things are going well, your Wii U should recognize the external hard drive in its data management screen in Settings.) If things are not going well, you might find that the WiiU suddenly cannot recognize your external HD and all your saved game data is apparently lost.
If you’re like me this could cause a panic, but luckily all may not be lost! There are a few additional things to keep in mind. By default the WiiU puts external HDs to sleep when they are not in use, but you can toggle this function off by going into data management, holding DOWN on the D-Pad for four seconds, then holding the plus and minus buttons. An option will appear to let you turn off the WiiU’s sleep function for external HDs.
If your content still doesn’t appear or your HD still isn’t recognized, try restarting the system once more. Check your connections to make sure they are snug, and after leaving the HD plugged in for a few minutes, reset once more. For whatever reason, my content suddenly appeared after doing all these steps in order. I will warn you not to futz with the external HD while content is running, as it may cause your content to crash.