The replacement sensor/ speaker I installed was bad also. Once I tried a working sensor, the phone did as it was supposed to.

So I have a samsung impression that goes dark as soon as you hit send when making a call. I know its supposed to do it when you put it up to your ear and cover the sensor, but it goes blank even just sitting there. The call still completes like usual, so I dont think its the flex cable because everything works okay and I tried swapping out the flex and the sensor/speaker for the top with the same result. Could I have gotten a bad sensor? Any other suggestions?