My 4s wifi is not working

I had this problem with a customers phone. The way in which it was supposedly to be fixed was with overheating the phone under a lamp so that the "needs to call down warning" comes up. This is supposed to reset the temperature information (or something ridiculous that makes no sense) but this has been apparently fixing it. So, yeah. I'd do a reset, restore, and update first. Or perhaps a backdate to iOS 6.x.x using tiny umbrella and installing with iTunes. Or, if you have SHSH blobs saved then change it back to whatever update you saved those blobs too :)

1. In Settings/General/Auto-Lock, set the iPhone 4S screen so that it permanently displays and does not switch off i.e. the 'Never' setting.

2. Use a hairdryer on Full to heat up the top of the iPhone around the headphone socket area.

3. After about 10 minutes, the screen will display a High Temperature overload alarm.

4. Stop heating, switch Off and place the iPhone in a plastic bag.

5. Place the bag into the freezer for 10 minutes.

6. Remove the iPhone from the freezer and allow to reach normal room temperature.

7. Switch On the iPhone.

8. The WiFi should now be working.

9. In Settings/General/Auto-Lock, set the iPhone 4S screen to the required display period e.g. 2 minutes.

10. On my iPhone this WiFi Restore method lasts for about 3 months before requiring to be repeated.