I replaced the screen on an iPhone for a customer in Mission tonight. As we were talking while I was replacing the glass on her daugter's iphone 4, the client mentioned how the Wifi and Bluetooth was no longer working after updating to iOS 7, the setting for both of the features were greed out.
I have had very good success repairing the issue on iPhone 4S. Every one of them have functioned after doing a simple trick of heating up the motherboard where the wifi chip is located.
I offered to the customer to look at the 4S once I was done with the iphone 4 screen replacement and within 15-20 minutes the problem was solved.
Here is a picture of the iPhone 4 prior to repairing it...
