1 Causes for both ambient light & proximity sensors not working?
Have an unusual repair job here, Verizon CDMA model iPhone 4 16GB factory white phone coming in having both ambient light and proximity sensors inoperative. Small shroud gasket from factory is intact (this is the thing people try to replicate with the black electrical tape). UV filter over proximity sensor from factory is intact. Believe the front screen to be non-OEM, back glass looks OEM. Phone appears unmolested internally (all screws of the right size in the right place). Water damage sensors white inside and on dock, red on headphone jack.
Replaced with known working power/sensor flex assembly from test phone. Again, both sensors inoperative in phone under repair. Everything else about the test phone is in normal working order.
Have swapped front glass from known working phone, still no joy on test phone with either sensor.
What could be potential causes for this problem?
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OK, I solved my own question. Posting here for others. So this kind of problem, as I suspected, was due to logic board physical damage. Most likely when a previous person changed out the original front screen for the current aftermarket one.
There was an SMD component missing, knocked off, the board adjacent to the connector that was the cause of the inoperative states. Put it under the microscope to confirm, and transferred this component from a boneyard board and it's working fine now.
por drshock