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Proximity Sensor: Mobile Phone Spares
The proximity sensor detects when the phone is held against the ear during a call and turns off the touchscreen to prevent accidental input from cheek contact. It is a small infrared emitter-detector pair mounted near the earpiece. When it fails, the screen stays on during calls — draining the battery and triggering unintended button presses.
Technology and Placement
A proximity sensor emits a pulse of infrared light and measures the return signal. When an object — the user's face — is within approximately one to three centimetres, the IR reflection intensity crosses a threshold and the sensor signals the phone to blank the screen. The sensor is typically positioned in the top bezel alongside the earpiece and ambient light sensor, often in the same flex cable assembly.
Failure Causes
The most common cause of proximity sensor failure after a screen replacement is the sensor not being correctly seated against the light-guide channels in the display frame — ambient light floods the sensor, saturating it and preventing it from detecting the face properly. Debris over the sensor aperture and a cracked front glass diverting or blocking IR light also cause failure. Genuine sensor hardware failure is less common than installation-related causes.
Diagnosis
Testing proximity function using a diagnostic app or by covering the sensor with a finger during a call identifies whether the sensor is responding. If it responds to a finger but not during calls at the ear, the issue may be the sensor position relative to how the phone is held rather than the sensor itself.
Repair in Nairobi
Proximity sensors are frequently sold as part of the earpiece/sensor flex assembly. Cost: KES 300 to KES 800. Labour: KES 400 to KES 700.
