Chosen Solution
Hi there I was in the believe that a batery change was the only problem with the iphone 5s when it turned hot and said it has to cool down before i could use it again. I changed the battery just to find out the phone crashes all the time, the phone boots up some times when pluged into charger, and some times i have to hold power and home button to get it boot up. Do anyone have a clue to what issues i´m facing? Regards from Denmark
Hello Carsten. If you are confident that you have used a known-good quality replacement battery, then I would ask where is the excess heat on your device? There are 4 thermistors on the logic board (forehead, RCAM, Baseband & CPU) so if anyone of those areas detects excess heat, it will send you that error message. So wherever the heat is, that is probably where the problem is. It is unlikely that the thermistors themselves have failed although it is not impossible. More than likely, there is high current going through one of those areas due to a partial or full short caused by a bad component or module. To eliminate any issues with the camera or front screen (forehead), remove the logic board and connect only the charge port and battery and see if iTunes sees the device. Then progressively add the screen (no fcam), home button, fcam, rcam etc until the message shows up. If it is in the baseband or or CPU area, the message will appear quickly. Your problem will either be modular (i.e. camera) or logic board.
