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Why does my iPhone's screen dim and go dark?

This is quite a common complaint for those who use their iPhones as an in-car satnav or for taking videos or flying drones -- especially in summer. And that's a big clue.
Written by Adrian Kingsley-Hughes, Senior Contributing Editor

Over the past few weeks, I've received a lot of questions from readers complaining that their iPhone's display is dimming to the point of almost being unreadable. Several of the readers were using their iPhones for in-car navigation, some were recording video, another was flying their drone using an iPhone connected to the controller, and some weren't really doing anything in particular.

This is quite a common problem, and one that's been plaguing drone operators for a long time. The screen on the iPhone will dim quite dramatically, to the point of making it almost impossible to read. And to make matters worse, you can't turn the brightness up. 

On top of that, there will be a lag and the iPhone will appear to struggle to work as normal.

So, what's going on here?

Well, there's a common theme here -- it's summer and the iPhone is getting hot.

Also: Using your iPhone in high temperatures can cause permanent damage

And if you know anything about iPhone behavior, you'll recognize this as a default strategy that the iPhone adopts when it gets too hot.

Several things happen when the iPhone gets too hot:

  • Charging, including wireless charging, slows or stops.
  • The display dims or goes black.
  • Cellular radios enter a low-power state. The signal might weaken during this time.
  • The camera flash is temporarily disabled.
  • Performance slows with graphics-intensive or augmented-reality apps or features.

Carry on using the iPhone and there's a chance that it will show a temperature warning screen and block pretty much everything.

OK, so what do you do in this case?

Cool down the iPhone. 

Bring it into the shade, place it over the cooling vent with the air conditioner on, or if you're out and about flying a drone, then it might be a good idea to fit a sunshade over the iPhone.

Once it cools down, you can get back to using your iPhone again.

Just try to keep it from getting too hot again. Or, you've guessed it, the screen will dim again!

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