We have a lot of repair shops that buy from us and I have heard all of these methods working on certain iPhones. I think it really depends on the iPhone. There is another method not mentioned here of the little lens that you put over the sensor before you install the new screen. We have them for less than $5 and they will fix the problem. I would try all of the free fixes first but if that doesnt work you can find the [http://www.etechparts.com/Proximity-Sensor-Cover-for-iPhone-4-p/822-4326.htm|iPhone 4 Sensor repair lens] [http://www.etechparts.com/Proximity-Sensor-Cover-for-iPhone-4-p/822-4326.htm|here].