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Water damaged iPhone 4S. Only working whilst plugged in.

I am currently working on a repair for a water damaged iPhone 4S.

Brief history: It was dropped down the toilet whilst the toilet water was clean (so less damage) about 3 days ago. The father put it in rice, which is pretty much useless but worth a try but the phone still did not turn on.

At the moment: I have cleaned it in Isopropanol alcohol after taking the cages off the motherboard. At first I did it with a tooth brush and then I put it in an ultrasonic cleaner with the alcohol in. I then went over the gold connection plates with an eraser to get all of the dirt and corrosion off them. After assessing the corrosion the motherboard seems pretty much near enough perfect (for what it is) but it still only comes on when plugged in. Obviously at first I thought this was a battery issue so I replaced the battery which should have had not much charge in it but the iPhone 4S says that the both batteries have 100% which doesnt prove true when checking with a multi metre. So both batteries are perfectly fine but the phone still only turns on when plugged in and straight off when taken off the mains. I have assessed the charging block and this is fine and also the power button is working perfectly (at first it was stiff but I have fixed this to see if it was the issue).

I think it may be a board issue in the sense that the power from the battery isn't getting to the board but the battery connections are fully intact and functioning.

Any ideas?

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Deck the Halls
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Chosen Solution

This is going to be corrosion under the battery connector. Desolder it and replace with a new battery connector. I've also been surprised when a 4S with relatively recent water damage kept doing random auto re-boots. The board looked fine after reflowing all corrosion.

On that one, I read the logs when it would randomly restart--it wasn't getting a temp reading, which is the job of one of the middle battery pins. Took off the battery connector and that was the problem. New connector solved.

Yours is likely the same case since the other job of the middle pins is battery percentage 'gas gauge' If yours is wrong with a known good battery, then that points a finger at battery connector, as does the fact that it won't boot from a known good battery.

Replacing connector will likely solve.

jessa

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Most Helpful Answer

SaraMai, the very first thing you want to do is to definitely proper discard the water damaged battery. Do not use it at all. Next I would suggest that you do get a new dock connector since it may have gotten damaged.After that, check your battery connector and check the traces, it is possible that you have a short in that particular area. In particular check 3 inductors. For that, of course, you need a multimeter, or at least an ohm meter, to check for continuity. I hate to refer to those as fuses, but they most certainly control part of the charging circuit. First one is reference designator L3, it is a FERR-120-OHM-1.5A inductor. L4, right below it , has the identical value. Next would be the charger inductor L28 2.2UH-1.8A-155MOHM. All of these are pretty much available at mouser. com or digikey.com. Check the Diode D604, located just above L28. Hope this helps, good luck.

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