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Screen stays black after a call (problem with proximity sensor)

What is the proximity sensor?

The proximity sensor detects when there is something (or someone, such as yourself) close to the display of your phone.

Without a proximity sensor, your phone would not know when you are putting the device close to your ear when you make a call and when you want to look at it (to activate the speakerphone or mute the call for instance).

Basically, if your display stays dark during a call and you cannot hang the call, mute it, put it on hold nor access the keypad, then keep reading!

 

Where is it?

The proximity sensor is part of the Top Module of the Fairphone 2. From the outside, and as depicted in the following picture, the proximity sensor area is located in the top left corner of the display.

 

How does it work?

The proximity sensor embedded in your phone combines both the emitter and the receiver of a non-visible light beam. If the light beam is received back in the phone, it means that there is an object somewhere facing your display. To know if this object is close or not, the intensity of the light beam (its brightness) is compared to reference values. That way, the phone is able to know if there is an object, and if it is actually really close to the display

 

So, what is the problem? And how to solve it?

The problem is that the sensor does not believe there is an object close to it because something is interfering with the emission and/or reception of the light beam. To solve this issue, we need to make sure that the light beam path is clear.

First you should check that your proximity sensor is really not behaving as expected: install a sensor-testing app, such as Sensors. Head to the proximity sensor readings: in Sensors, swipe from the left edge to the right edge of the screen, select Proximity.

The Fairphone 2 proximity sensor should report “5 cm” when there is nothing close to it (left picture), and “0 cm” when there is (right picture). You can easily check that it works by covering and uncovering the upper side of the display with your hand, the proximity sensor value should change accordingly.

 

The proximity sensor is working, so why does the screen stay black?

If the sensor is reporting the right values when you play with it, then you may still experience the issue from time to time when the upper side of the display is not clean enough (see the next section).

Pay also attention, if you have previously removed the display, that it is properly back in place. This is most noticeable in two places: 1) the front camera is not properly centred in the display “lens”, and 2) the display is not aligned with the chassis (see pictures below: the left device is properly closed whereas the right device has a gap between the display and the chassis).

 

The proximity sensor is not working as it should

Clean the outside of the display

If the issue happens while you are on the phone and you are looking for a quick solution, you should first try to clean the display (with your sleeve for instance), bring the phone back to your ear, and take it away again. It might be that the display is just dirty and impairing the sensor reading.

Try again the sensor-testing app to see if you just solved your issue.

Pro tip: Once you have the chance, you should properly clean the display with a microfibre cloth and a display cleaning product.

Clean the inside of the display

If the sensor is still not behaving as you want it to be, you will now have a look inside the phone. Check out our video on how to replace the display if you have never removed it before.

With the help of a thin microfibre cleaning cloth (or any no-lint cloth), make sure the inside of the sensor “lens” (circled with orange in the picture below) is clear of any dirt/dust.

Once more, try the sensor-testing app to see if the issue is solved.

Calibrate the proximity sensor

Starting with Fairphone OS 1.6.2, we released an app to calibrate the proximity sensor of your device in three simple steps (cover the sensor, un-cover the sensor, reboot the phone).

To calibrate the proximity sensor, follow our lead:

  1. Update your Fairphone 2 to the latest Fairphone OS available;
  2. Start the Proximity Sensor Tool app from the phone Settings > Maintenance > Proximity sensor;
  3. Follow the 3 steps to calibrate the proximity sensor;
  4. Reboot your device as explained at the last step, you're done.

 

If you still experience an issue, please contact us!

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