Answer to: Is a iPhone 4 logic board needed?Yes, yes, yes! The logic board is your power management brain. I am surprised that you have had such good success so far without it. Apple calls their motherboards, "logic boards" but it does the same thing. So essentially you are using a phone without the motherboard installed. The processor, and most of the sensors are separate in the iPhone (compared to laptops where the logic board contains just about every major part besides RAM and a Harddrive), but it is still mainly there for power management. Now it is different from the battery and the power supply charger, so they still will work at some very low level, depending on what they were doing when you disconnected it, but you will have major problems charging it and possible sensor communication errors. The $10 fix will be well worth it, otherwise you might as well get used to using your phone plugged into the wall.