Try taking the fan apart and and seeing if hair or build up is slowing it down if not it might be a short in the wiring. to fix it try returning it to see if you can exchange it or call the company and have them see whats wrong with it

cheryl i have studied the nintendo for years. i took it a part i fixed all of my ds's you hold the power button for exactly 62 seconts and it will turn on but im still working on nintendo3ds for ever cant find souloution.