The iPhone 4 power & sensor cable is a part that commonly needs to be replaced, it's used to turn the iPhone 4 on & off and also controls the proximity sensor. It is susceptible to damage from water, corrosion and over use or mechanical failure. If you frequently use your iPhone 4 while in the rain and sometimes if you are in a very humid environment and keep the iPhone in your pocket, the iPhone 4 power & sensor cable circuit will absorb water and become corroded. Mechanical failure happens when the tiny convex disc that completes the circuit when you press the button loses its ability to spring back to its original shape. This part is responsible for the clicking noise you hear when you press the button, so it is easy to diagnose that particular fault. Our tech has written some information below on how to diagnose a bad power / sensor flex cable and should be enough info for you to know if this is the part you need to fix the problem.
How do you know if you need to replace your iPhone 4 power & sensor cable?
Here are a list of common symptom indicating a problem that can be repaired by replacing the iPhone 4 power & sensor cable:
iPhone 4 won’t turn on with the power button, but turns on when plugged into a charger.
iPhone 4 won’t turn off.
iPhone 4 comes up with the ‘slide to power off’ screen without pressing the power button.
iPhone 4 turns on by itself without pressing the power button.
During a call, iPhone 4 screen doesn’t go dark. (faulty proximity sensor)
During a call mute, speaker or other buttons are pressed with your cheek. (faulty proximity sensor)
After a call, when the iPhone 4 is not at your ear, screen stays dark. (faulty proximity sensor) (also check for dirt on the screen next to the earpiece speak grill and try removing any mirror screen protectors)
Symptoms that appear to indicate a faulty iPhone 4 power & sensor cable but are actually caused by other components.
iPhone 4 won’t power on with the power button and also won’t power on when plugged into a charger. (this is caused by either a faulty battery or faulty dock connector. If the battery is faulty you should see a flashing apple logo appear before the iPhone 4 turns off)
iPhone 4 won’t power off and screen won’t respond or there is a small loading icon in the centre of the screen. ( Usually a software issue )
iPhone 4 won’t power off. Displays the ‘slide to power off’ screen, but won’t slide. (usually a faulty touch screen)
iPhone 4 screen stays dark all the time, not just during calls. (faulty lcd or lcd power coil)
You should also be aware that it is rarely the chrome button that you press that is at fault. It is almost always the iPhone 4 power & sensor cable underneath the button. The difficulty level for replacing this part is similar to that of replacing the lcd + touch screen digitizer. You will need to go through most of the same steps, until you have removed the logic board. The repair is not particularly difficult, but if you haven’t repaired an iPhone 4 before you need to be aware that there are many breakable parts if the install is not done correctly and with enough care.