New iPhones May Be Prone to Overheating

The new Apple iPhone 3GS is hot. So hot, in fact, that Apple has built in a kill switch that won't let you use it once it hits 113 degrees.

Reports began circulating online last week that the latest iteration of the iPhone got noticeably warmer than its predecessors. And photos popped up on a French tech blog of iPhones so hot their white exteriors were glowing pink.

Then two respected American tech reporters confirmed the rumors were true -- because it had personally happened to them.

"At some point, I became aware the handset had become very hot," wrote PC World's Melissa J. Perenson on Friday. "Very, very hot -- not just on the back, but the entire length of the front face, too."

"One does not ... expect to reach under one's pillow and find an iPhone that passes for a handwarmer," wrote her colleague David Coursey on Monday.

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Coursey later took his handset to an Apple Store, where the technician told him there was an internal sensor that prevented the phone from being operated if its internal temperature hit 45 degrees Centigrade, or 113 degrees Fahrenheit.

It turned out Apple had already posted an advisory on the issue, complete with a screen shot of the heat warning.

The company asked users to avoid risky situations, such as "using certain applications in hot conditions or direct sunlight for long periods of time, such as GPS tracking in a car on a sunny day or listening to music while in direct sunlight."

In other words, if you're cranking the iTunes on the beach, put the iPhone under an umbrella or it might stop working.

Apple, in fact, may have tried to avoid the problem by slowing down the iPhone 3GS's main computer chip.

A couple of "teardowns" detailed on the Web revealed that the CPU had been "underclocked" to run significantly slower than its native speed.

The tech bloggers who found it assumed the slowdown was to preserve battery life, but since CPU speed is the main generator of heat in any computer system, it would help keep down the iPhone's internal temperature as well.

Coursey wondered whether a recall might be worth exploring, though he added he'd heard rumors Apple would exchange units that had tripped the internal sensor. The Apple Store technician told him his hadn't.

Requests by seeking comment from Apple were not immediately returned.