Original post by: moa ,
here is what you do , i had same problem I just opened back cover and tightened the small screw behind the sensor and worked better than when i bought it knew . the screw get loose when dropped and the screen gets raised up and block part of sensor and and light do not get to sensor . try it, it worked for me like charm for me . the sensor works better than when i bought it , the phone sensor responds in less than a second. good luck.