Recently, customers keep reporting that they have problems with proximity sensor after they changed the screen assembly on iPhone 4. We did some test trying to find the reason.
1.we test proximity sensor in a sample iPhone 4 and it works fine.
2. test 20 pcs copy screen assembly(10 white,10 black) and 20 pcs original ones(also 10 white and 10 black),works fine
3. Put the copy screens one by one in the working device. Only 5 out of 20 works, 3 black and 2 white
4. Try the original screens one by one and test. Only 6 of them passed. 3 white and 3 black.
Seems the front LCD screen w/d(light sensor window) and light sensor cable doesn’t match each other well. Help!
Then one day, all by chance, when replacing a broken screen(original), the repair man found a small foam sitting on the sensor window of the broken panel. It was too tiny to be noticed. Will this foam the key to solve the proximity issue? In no time,we replicated it with some tape. Put them on the screens that failed in the test we did earlier and tested again. All works fine! My salute to Apple’s great engineers!
Hope this helps!