Answer to: iPhone 4s greyed out wifiI have ran into this problem before on different 4S iPhones. The problem is with the solder touching around the wifi section of the logic board. Usually due to a lot of usage and the heat generated caused it to separate. With the phone turned on.. I used a hair dryer and heat the back of the phone up until I saw the Temperature Overheat Warning flash on the screen. Instantly, I turned the phone off and put the phone in a sealed zip-loc bag and placed it in the freezer for 10-15 minutes. After that, no problems.