my iphone 4s wifi is greyed out

Ok, I have found a temp. Solution - here is what makes it work again - for about 2-3 months - you need to take it to a technician and let him take it apart and heat the board with a heat gun - after that allow it to cool and then reassemble - that will work for 2-3 months. Apple like they had a defective batch made - they need to recall all and replace them. Its a dry joint somewhere on the circuit board so the heat fixes it temporary. Do not waste time with the software - it's the hardware that is not working.

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FaceTime not recognizing my apple ID wrote:

Ok, I have found a temp. Solution - here is what makes it work again - for about 2-3 months - you need to take it to a technician and let him take it apart and heat the board with a heat gun - after that allow it to cool and then reassemble - that will work for 2-3 months. Apple like they had a defective batch made - they need to recall all and replace them. Its a dry joint somewhere on the circuit board so the heat fixes it temporary. Do not waste time with the software - it's the hardware that is not working.

This solved my questionThis helped me

Your technician did not rework the solder correctly if it is failing again.

This is the real fix.

http://www.ifixit.com/Answers/View/135053/WiFi+Greyed+out+iOS+6.1.3

You have to heat the Wi-Fi chip to rework the solder and then the Wi-Fi chip works again. The problem was caused by iOS 6 which allowed the Wi-Fi chip to overheat.

I have just confirmed that this is 100% a hardware problem via my own similar problems, research and final fix.

There is no possibility that it is an OS problem, it is a hardware problem that is caused by a lack of attention to detail during the manufacturing process.

The problem actually lies in the poor quality of solder that was used during the manufacturing process of the iphone 4/4S.
The solder connecting the WI-FI chip to the circuit board deteriorates over time.
The only fix is to re-heat the solder so that it regains it's conductivity (for a time).
This is why the "Heat with a hair dryer / place in a freezer" fix actually works.
I was loath to do this as it sounds like a crazy thing to do, but I tried it as a last resort and hey presto!......it worked.

BUT.....of course over time the solder will deteriorate again and I will have to do the same again.
Apple's quality control missed this vital element of solder quality and thousands, if not millions of us are paying the price, especially because the problem manifests after the guarantee has run out.
Apple is of course staying very quiet about this.

This problem will also have long term environmental impact, as a lot of users will just give up, throw the old phone out and buy another.
Maybe a class action against Apple in relation to this problem is in order?