CPU is getting abnormally hot
So my friend dropped her 5S in a pool and I have no idea if she immediately turned it off and put it in rice or not. She gave me her 5S in hopes of reviving it. I took out the logic board, soaked it in 90% isopropyl alcohol for a day, replaced the battery, and cleaned out any corrosion that I saw. I reassembled everything back together and notice that the middle of the screen has lost touch functionality and that the CPU was getting abnormally hot and killing the battery life, which to me indicated a short circuit. I tested this with 2 other spare 5S screens I have on me and they both exhibited the same problems.
Since I'm not an expert with SMD soldering and risk messing the board up even more, I bought another 5S logic board on eBay that had no water damage or any problems. I install the board and the screen has full touch functionality and everything went well. Except that the CPU is still getting abnormally hot and making the battery life really bad. It gets too hot to touch the phone sometimes and it stays hot even if the phone is sleeping so this is not the normal operating temperature of the phone.
So I think to myself, what could possibly be making this CPU heat up so much? Could it be the dock connector? Or is it the replacement battery that could be making it do this? I replaced the logic board and inspected it to make sure it wasn't water damaged which it wasn't. It just confuses me so much right now. All help would be appreciated.