Instructions
Remove the AC adapter from both the system and the outlet. Leave the adapter unconnected for at least two minutes.
Disconnect all controllers, accessories and memory cards. Make sure nothing is plugged into the USB slots while troubleshooting the AC adapter, as these draw power from the Wii.
Plug the AC adapter directly into a wall outlet (not a power strip or surge protector).
Consider replacing the AC adapter with either a used AC adapter. Contact Nintendo's Customer Support (see Resources) for further help.