So you mean the screen turns off on its own all the time?
It is reducing battery life which is already poor.
How can i de-activate it ?
It should be activated itself only when there is incoming phone call.
If your screen is not actually turning off if you put your face near it, then I would say that it's not activated.
I know what you are saying with the light, but unless its actually disabling the screen, then I would say its normal behavior .
I've disable auto brightness. The red light is still on. And by touching the screen, it glows stronger...That is the brightness sensor, not proximity. And yes, it is always on.