The proximity sensor has nothing to do with the auto-brightness feature. It is used to disable the screen when you make a call; it will detect that the phone is pressed against your cheek and close the display so that the digitizer doesn't register any touching.
During the previous repair, it is possible that the prox sensor was incorrectly positioned or possibly even damaged. It is part of the FCAM flex. You can check that yourself via this [guide|75241|guide].
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As for the auto-brightness, that function was moved to the Accessibility menu.
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As for the auto-brightness, that function was moved to the Settings/General/Accessibility/Display Accomodations menu.
The proximity sensor has nothing to do with the auto-brightness feature. It is used to disable the screen when you make a call; it will detect that the phone is pressed against your cheek and close the display so that the digitizer doesn't register any touching.
During the previous repair, it is possible that the prox sensor was incorrectly positioned or possibly even damaged. It is part of the FCAM flex. You can check that yourself via this [guide|75241|guide].
As for the auto-brightness, that function was moved to the Accessibility menu.