iPhone XS Max overheating often housing change

Housing replacements can open up a pandora’s box of issues. The biggest challenge is transferring everything over without damaging any flexes, connectors or components directly on the logic board. The golden rule of troubleshooting is to only change one thing at a time but with a housing replacement, that becomes impossible.

Before anything else, do a thorough inspection of the board and flexes. Look for anything, even the tiniest tear or damage as that is all it takes to cause issues. Use magnification if your eyesight isn’t up to snuff or to confirm any suspicions.

Afterwards, I would try a bare bones approach. Remove the logic board and charge port, and build out a basic phone on the workspace. Connect the charge port, screen and then the battery and let the device boot by plugging in a charger. See how the phone behaves and look for excessive heat signatures. Keep in mind that the board will be hotter than expected because the case is not there to mask (and sink) the heat created.

Assuming all goes well, start adding modules one at a time and test after each one. At some point, you will notice a different heat signature and that will tell you which module is causing the issue.