Some things to try first:
1. Turn Off your iPad. Then turn Off (disconnect power cord for 30 seconds or longer) the wireless router & then back On. Now boot your iPad. Hopefully it will see the WiFi.
2. Go to Settings>Wi-Fi and turn Off. Then while at Settings>Wi-Fi, turn back On and chose a Network.
3. Change the channel on your wireless router (Auto or Channel 6 is best). Instructions at http://macintoshhowto.com/advanced/how-to-get-a-good-range-on-your-wireless-netw ork.html
4. Go into your router security settings and change from WEP to WPA with AES.
5. Renew IP Address: (especially if you are droping internet connection)
• Launch Settings app
• Tap on Wi-Fi
• Tap on the blue arrow of the Wi-Fi network that you connect to from the list
• In the window that opens, tap on the Renew Lease button
6. Potential Quick Fixes When Your iPad Won’t Connect to Your Wifi Network
Wi-Fi Fix for iOS 6
iOS 6 Wifi Problems/Fixes
How To: Workaround iPad Wi-Fi Issues
Another Fix For iOS 6 WiFi Problems
Wifi Doesn't Connect After Waking From Sleep - Sometimes increasing screen brightness prevents the failure to reconnect after waking from sleep. According to Apple, “If brightness is at lowest level, increase it by moving the slider to the right and set auto brightness to off.”
Fix For iOS 6 WiFi Problems?
Did iOS 6 Screw Your Wi-Fi? Here’s How to Fix It
How To Fix Wi-Fi Connectivity Issue After Upgrading To iOS 6
iOS 6 iPad 3 wi-fi "connection fix" for netgear router
Apple's iOS 6 Wi-Fi problems
How to Boost Your Wi-Fi Signal
Troubleshooting a Weak Wi-Fi Signal
How to Fix a Poor Wi-Fi Signal on Your iPad
iOS Troubleshooting Wi-Fi networks and connections http://support.apple.com/kb/TS1398
iPad: Issues connecting to Wi-Fi networks http://support.apple.com/kb/ts3304
WiFi Connecting/Troubleshooting http://www.apple.com/support/ipad/wifi/
How to Fix: My iPad Won't Connect to WiFi
iOS: Connecting to the Internet http://support.apple.com/kb/HT1695
iOS: Recommended settings for Wi-Fi routers and access points http://support.apple.com/kb/HT4199
How to Quickly Fix iPad 3 Wi-Fi Reception Problems
iPad Wi-Fi Problems: Comprehensive List of Fixes
Connect iPad to Wi-Fi (with troubleshooting info)
Fix iPad Wifi Connection and Signal Issues http://www.youtube.com/watch?v=uwWtIG5jUxE
Fix Slow WiFi Issue https://discussions.apple.com/thread/2398063?start=60&tstart=0
How To Fix iPhone, iPad, iPod Touch Wi-Fi Connectivity Issue http://tinyurl.com/7nvxbmz
Unable to Connect After iOS Update - saw this solution on another post.
Note - When troubleshooting wifi connection problems, don't hold your iPad by hand. There have been a few reports that holding the iPad by hand, seems to attenuate the wifi signal.
If any of the above solutions work, please post back what solved your problem. It will help others with the same problem.
I have had the same problems on my iPad 3 with both iOS 6.1.2 and 6.1.3. At home the iPad connects fine to my airport extreme 5ghz (WPA2) network. But I cannot connect to public WEP networks unless I am only arms length away. This was true a month ago while I was in Mexico on 6.1.2 and now back home with 6.1.3. Useless for travel!
Support told me they would exchange it for another. Might as well do that as all data was wiped attempting to solve the problem! I suspect the problems is the 2.4 ghz radio or antenna. It is a hardware issue which seems to occur with non Apple networks. Don't travel with it unless you also bring a windows netbook! My iPhone 3GS on 6.1.3 connects fine to the same problematic hardware. Hope this helps.
Just wanted to update my post. Today I picked up a replacement ipad 3 from the Seattle Apple Store. It is build DKVJW. It shipped with 5.1.1. I set it up and successfully logged on to my 5ghz Airport Extreme network which uses WPA2. I upgraded the OS to 6.1.3. Once again it logged on to the home network. But the real test will be when I attempt to use a public network in the 2.4ghz spectrum with WEP. That test was successful. I was able to view the networks available at my local food coop and join a 2.4ghz WEP secured network. First attempt.
The build on the ipad 3 which could not connect was DKWJ. The ios 6.1.3 (10B329) was the one I installed in the replacement ipad. Hope this will help someone sort out their connection issue.
My problem was solved by a new replacement iPad 3. It shipped with 5.1.1 and when upgraded to 6.1.3 it worked fine on both my home network (Extreme 5ghz/WPA2) and local hotspots (non-Apple 2.4ghz/WEP.)
For anyone posting problems try to be specific on what type of networks work, and don't work. Check to see if it will work within arms length of the specific router and report that. Unless the variables are listed it is really hard to help out.
My router is within arm length and it still gets disconnected. My network is 5ghz with WPA2 both networks, Cisco 3500 access point and the ATT Uverse router. They both sit next to each other. They can't affect each other due to they broadcast different SSIDs. My Windows Laptop is not having issue staying connected to either network from any distance away.
The Only way to conclude that it is a Hardware problem is when the iPad is downgraded back to iOS 5 and the wifi still does not work.
I have my iPad 2 for one n a half years. If it is hardware problem, either i m a screw up user or it just says so much about apple's product quality, given the number of cases of wifi problem.
The Apple service shop refreshed 6.1.3 for me, cannot connect to wifi n concluded its hardware problem. Asked me for 400$ to get a replacement. To me this is BS.