Why would proximity sensor fail after camera & battery replacement?
iPhone 4, 16GB, black, AT&T, early model
It's been a difficult month for my phone and me: My LED flash stopped working, so I decided to replace the rear facing camera unit. (Having repaired numerous iPods and other cell phones, I thought I was up to task.)
I followed the iFixit guide and replaced the camera unit, but I soon found that the reception (especially wifi) was not good. I had noticed the precautions regarding finger oils and had used a cotton swab and glass cleaner to clean the grounding points during re-assembly, but I thought maybe I hadn't done it correctly, or something wasn't seated correctly.
I took the battery and wifi antenna/contact shield back out, and then used a liberal amount of contact cleaner on all the contacts and ground points. Unfortunately, I must have used WAY too much contact cleaner (or I let the contact clip fall into the wrong place at the wrong time), because when I was attempting to reconnect the battery--POOF! A tiny blue flash and a tiny puff of smoke. This of course led me to replacing the battery the next day, and fortunately, the phone started up again after replacing it.
Now everything seems to be working fine except the proximity sensor. (It doesn't disable the touchscreen when I'm on a call and place the phone to my ear.) I've tried it with and without the case. I'm using a Zagg screen protector, but it has the cutout for the sensor, and it is unchanged in the repairs I've done. Most of the reports of proximity sensor problems seem related to the replacement of the screen, but I haven't removed the screen or anything deeper than the rear camera. I've tried restoring the phone software (from a backup) to no avail.
Is it possible that when I killed the battery I also killed the proximity sensor? It seems like some other parts would have failed as well. Also, I overtightened the 1.4mm screw in the wifi antenna (circled in yellow in this photo ) and caused the boss to come loose. I was able to tighten it by holding the boss with tweezers, but this still might be a problem source. Before I order a new proximity sensor and tear the phone completely apart to replace it, does anyone have any other ideas of what could be causing the problem? Any way to test to confirm that the sensor itself is dead? Given how finicky these sensors seem to be (and the problems I have caused myself in other repairs), I'd love to get some feedback and advice before I take on the task of replacing it.