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Depending on where the Wii was purchased from, you may be able to take it into the retailer and exchange it. For instance, if it was purchased from Game Stop, they are very amenable to replacements. Especially if the Wii is only a few days or weeks old.
If the retailer is not an option, Nintendo itself gives a 1 year warranty on parts. If you want to restart a repair request through nintendo, t his page will walk you through that process.
Keep in mind, a warranty repair takes time. Time to ship the device off and for them to ship a replacement.. Usually between 3-6 weeks. In the meantime, you may want to consider purchasing a generic replacement controller at a discount, such as this one. http://amzn.to/1maXsia
That way your son has something to use in the meantime.
if you have further questions or concerns, let me know.
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