Had this also when replacing a pre assembled screen. I took al the parts from the original screen and assembled them on the new screen. Then the problem was solved. What i always do when i run into these kind of problems is just boot the phone with almost no flex cables connected. Then step by step connect a flex and test again. Try to isolate the problem this way.
Im also totally confused with this problem. I have a iphone4 tried 3 different screens and it keep having this effect. Frame is completly clean. Later i removed the adhesive, didnt help either. Played around with tighting ans loosen the screws. No result either. I dond understand this. Btw this is not my first phone i repaired. I did hundreds already. But this.... I have never seen before...
replacing your sensor doenst work, just what i do is use some paper tape and make it black with a marker and put it on top of the sensor, When playing around with darkening the sensor always do a reset on the phone before testing!I had a situation that after the adjusting it didnt worked. then reset the phone and it was there again! already fixed a few of them this way!
Wow lots of theories, What about this problem, The sensor didnt work anymore after a screen replacement. I replaced the sensor flex. No Result Checked for the foam, it was still there, put a layer of tape on top of it. No Result Replaced the OEM front with a original Apple from a working iPhone. No Result. Any ideas, this problem is so strange!
I always use the screwdriver that is sold for repairing iphone. But these screw look a bit different from what i have seen. BTW the first batch op iPhone4 came with these screws. Mr Jobs decided to change this because repair company's started doing repairs and consumers opening their iPhones. Then they replaced them with the pentalobe.
Depending on your soldering skills you could also use liquid silver. It is really easy to apply and is made for situations like this. I often do iPhone repairs and find this very usefull. But keep in mind that this stuff is more expensive then soldering, i paid €30,- for it. Good luck
The only thing that mathers if you have the GSM of CDMA model. There could be a difference in there. I think the CDMA model is only used in Amerika, not sure. Over here we use GSM only so i only order the GSM version screens.
Check the cables is they are all clean, reconnect everything. If the problem is still there you could have a faulty unit. If it's not an option to send the unit back to the store, seller where you bought it from then open the two units. just use a screw driver to pry them open. once upen cut the speakers units loose, resolder the connection points with a short piece of wire. This could help.