The iPhone 4's proximity sensors are causing problems for some users. Macrumors reports on another issue (the more publicized being the signal reduction for left-handers) that has been popping up frequently involving the phone's proximity sensors.
The proximity sensor is what turns the screen off while making a phone call, it keeps the user from accidentally touching an icon while using the phone.
In Apple's official forums, the issue has been brought up and has grown to 63 pages of nearly 1,000 replies (941, to be exact). The original poster mentioned that while his sensor seems to work when he puts his finger over it, but when using his phone up to his face, the screen blinks on and off as if it "cannot decide to disable the screen or enable it."
Some reports indicate that the sensors will turn the screen on mid-conversation and inadvertently mute the call (though I've recently had something similar happen happen with an iPhone 3G running iOS4, resulting in an accidental speakerphone conversation). Others report that after a phone call their sensors do not activate the screen, resulting in a black screen when they pull away the phone.
Macworld also reported on the issue and said that many users have been able to correct the problem by either resetting their phone's settings or hard rebooting:
Many affected users report that either a Settings reset or a hard reboot fixes their problem. One Apple support thread recommends that users open the Settings app, then go to General -> Reset, and choose "All Settings" at the top (note: this will not erase your apps, media, or other data — that's what the "Erase All Content and Settings" button just below this option is for. "Reset All Settings" just reverts any Settings preferences you've customized back to their factory defaults). One Twitter follower, Brian Partridge, reported that AppleCare told him to just use Reset -> Reset Network Settings, not all settings, and it worked.
In addition, here are some recent tweets from iPhone 4 users regarding issues with their proximity sensors:
- michaelyuan Maybe Apple should fix actual problems on iPhone 4, such as the janky proximity sensor, instead of non-existent ones, like reception issues.
- macsmarts Here's a trick to people having iPhone 4 proximity sensor problems, if you've trying to use a 3GS case – the proximity sensor may be covered
- hardmac_dot_com got the iPhone 4 "proximity sensor bug" not 5 minutes ago… screen turned on because I moved the phone a fraction from my ear.
- troycovey Seriously considering returning my iPhone 4 and going back to the 3GS. Dropped calls like crazy and messed up proximity sensor.