I have done about 8 hours research on this problem. Very rarely does anybody talk about the software component of this issue. So frustrating. You can go to the fix at the bottom if you get bored
***The problem. Wifi is Greyed out (Wifi is Grayed out) It will come back on intermittently / at random and then drop out for long periods.
1/ It would seem if I put it in front of a heater, into the freezer it would work for a short period of time. (Thinking it was the chip solder problem)
2/ I found if I turned off WIFI, Cellular data, blue tooth, and put it into air-plane mode (you have to do all these things for the experiment to work and the stack to be rebuilt temporarily) Then fully turn the phone off (power it down) Wait a sec and then turn it back on. Then you can turn your data services back on. If you find that your wifi comes back on temporarily you may very well have a driver service interruption problem. The wifi/blue chip driver will restart ok but another service will start and cause a over flow problem.
***Explanation of how I found the problem
Anyhow I was frustrated that apple did not have a way of sending sms like the Samsung Kies software does. I went to the Apple store and installed quite a few programs that promised this functionality. None of them did.
So I uninstalled them all. A couple of days later when I rebooted my phone after a while the Wifi stopped working and would not connect. I then turned Wifi off and tried to turn it back on but it wouldn't. It just became Greyed out. That is where my problems started. (I didn't realise the 2 issues were related)
***The fix
After reading allot via mr Google I decided to reinstall my system via Itunes. I updated to the latest version of Itunes. (iTunes 11.0.4 for Windows (64-bit)
I did a restore from back up. (no luck (read no fix)
Looked at the update version (it wanted me to update to 6.1.3) (no go as I have read many people do this but the problem comes back after a couple of days to a week - so this possibly was not the solution (wanted to keep it up my sleeve)
******Back the **** up people and make sure the backup works*****
I then Jailbroke my phone via Evasion. Installed Ilux RAT via cydia and used option 12. (please note option 1 will not fix your problem)***Read the instructions*** and it worked. WARNING THIS WILL WIPE YOUR PHONE AND TAKE IT BACK TO VIRGIN JAILBROKEN STATE*** My wifi worked perfectly. I then installed my back up from Itunes to my phone. All is perfect in the world.
***Note, I love my iphone but it felt like a relic from the past in comparison with my wifes new Samsung Galaxy S4. I have realised that JB is the only way to have a usable iphone in the real world with the same functionality as a Android phone. I have since found a program that works perfectly to send and recieve sms from my computers browser. (the same as the Samsung Kies program) (Remote Messages 2 via Cydia) I was going to upgrade to a Iphone 5 or a S4 but I don't need to any more. I have also found AUXO, five icon dock, fullscreen for safari, ifile, ikeywi, Jaku theme, SBsettings, silent photo chill, Tab+, tap to widgets, TorchNC, Velox, WinterBoard and 3dBoard. All these add ons have fixed other bugs and frustrations. Life could not get any better. I am having a ball. I have heard people talk about Jail Break but never advocated it and I still don't, it is just now my personal choice. Apple get your act into gear. You are making millions but falling behind by a long shot. History dictates the winner always favours usability. IOS 7 looks ugly!
***Please don't flame me for this post, If you can find another alternative for fixing the problem for a phone that is out of warranty, then post it or shut up. If you have a problem with this post please be constructive. Please do not reply if you have not actually had this problem yourself. Paying $200 to apple for a well known problem that they are not fixing is not a option. If you don't believe me then spend some time doing your own research first.