I bought a 3DS XL on eBay last year that was advertised as fully functional, but the Wifi would not stay connected. I looked this issue up and people said either a loose Wifi card, a bad Wifi card, or a motherboard issue.
I cleaned the Wifi card in the system and that did not work. I tried changing some settings and that worked for maybe 15 minutes then it quit. I bought and put a used Wifi card in the system, and that seemed to work, but then it didn't.
So I am all out of options now and further Google searching indicates that it might be a faulty motherboard. I can buy a new motherboard for it for about $20, but before I do that is there anything else I can try? Is there some kind of setting I've missed or a programming issue?