An iPhone's Auto-Lock feature automatically turns off the device's display, also known as the backlight, after a set period of inactivity. If the feature's Never option is selected, the backlight does not automatically turn off. Choose a time limit from the Auto-Lock Settings screen in iOS 8.3 to turn your iPhone's backlight off automatically. However, if changing your iPhone's Auto-Lock settings does not correct the problem, restarting the device or restoring it to factory settings are steps that can recover the feature's functionality.
Auto Lock
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Step 1
Select the Settings icon from your iPhone's Home screen to open the device's Settings screen.
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Step 2
Select General from the list of settings to open the General screen.
Step 3
Scroll down the General screen and tap Auto-Lock to open the Auto-Lock screen.
Step 4
Select the time limit you want to use from the list of options, such as Two Minutes. The change is immediately effective.
Restart Your iPhone
Similar to a computer, restarting your iPhone stops all running applications and processes, one of which may be causing the backlight problem.
To Restart Your iPhone:
- Press the Sleep/Wake button and then hold it until the Slide To Power Off slider appears on the screen.
- Drag the slider to the right and wait for your iPhone to turn off.
- Press the Sleep/Wake button again and then hold it until the Apple logo appears on the screen. Wait for your device to restart.
Restore Your iPhone
Step 1
Open the Settings screen by tapping the Settings icon on your iPhone's Home screen and then select General to open the General screen.
Step 2
Scroll to the bottom of the screen and tap Reset to open the Reset screen.
Step 3
Select the Erase All Content and Settings option.
Step 4
Enter your iPhone's passcode -- if applicable -- in the Enter Your Passcode field and then tap Done. If you did not set up a passcode for your iPhone, the Enter Passcode screen does not appear.
Step 5
Enter your Restrictions passcode -- if you enabled the Restrictions feature -- in the Enter Your Restrictions Passcode field. The Enter Passcode screen only appears if the Restrictions feature is activated.
Step 6
Tap Erase iPhone from the pop-up menu and then follow the directions to restore your iPhone to factory settings.