Fourth generation iPhone. Repair is straightforward, but the front glass and LCD must be replaced as a unit. GSM / 8, 16, or 32 GB capacity / Model A1332 / Black and White.

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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.

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1 Answer

Most Helpful Answer

My advice, keep away from replacing the sensor. From personal experience i have found this job very time consuming and frustrating. As it is such a delicate part, it is very hard to replace successfully. I have attempted the replacement about 10 times, and have only succeeded once.

Before you start tearing your iPhone apart, take a look at this and skip down to question 17. Now the fact that your iPhone has started shooting sparks and smoke at you also can lead to the conclusion that your Logic board has short circuit. This may or may not be the reason for the faulty sensor, but if it saves you paying $800+ for a new iPhone then it is worth a shot i guess ;)

Don't worry about that yellow screw placement, it will not effect anything whatsoever. Also why did you use Glass Cleaner??? You shouldn't use anything other than Isopropyl alcohol when cleaning electrical components as it removes oil/corrosion and evaporates very quickly. This could be another cause as the cleaner may not have evaporated completely when the battery was reconnected.

Before you do anything, make sure your iPhone is not under warranty, because if it is then you will be able to get the entire unit replaced for free.

Hope this helps!

Martin

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Comments:

Thanks for the advice, Martin. I decided to bite the bullet and go in for a replacement/upgrade. (I got the phone in October 2010, so it was long out of warranty.) Fortunately, the replacement was "only" $150, and I didn't have to use my upgrade eligibility on the 4S.

As for the glass cleaner, I only used it because it was specifically recommended in the iFixit guide! (See Steps 6 & 8.) I thought this was strange as well, which is why I went back in with DeoxIT. I think the isopropyl alcohol is a much better idea.

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