Chosen Solution
I recently received an iPhone X from a customer. They said that they had issues with the phone turning on. It only turned on for 15 seconds (when connected to power only) and that they got a new battery fitted, and it still didn’t work. I do suspect a faulty battery. However, could something else be causing this issue?
If we go with the theory that the replacement battery is good but just didn’t help the issue, the next most likely culprit will be the charging flex assembly. As @strongbow mentioned, if you’ve got a replacement battery on hand you can test it just by plugging it in and seeing if it makes any difference. You also might be able to see if the phone will take a charge by trying a wireless charger since it uses an entirely different circuit path to the motherboard than the charging port does. By the way, when the phone is plugged in, is there any battery charge indication? I know on a dead battery the first thing that happens is the battery display showing a thin red line indicating a very low charge. Do you get anything like that in the short time it’s powered on?
