On Aug 16, 2011, at 3:57 AM, Nick Adams wrote:

> Greetings,
> 
> Normally my Mac temperature is around 137ºF and if it is a real hot day, it 
> may rise to 139º F. The fans usually stay at a constant rate.
> 
> A few days ago, a few minutes after booting my computer in the morning, the 
> temperature started rising above it's normal range and rose to around 140ºF 
> and rising, the fans kicked into overdrive.
> I immediately restarted the Mac and everything returned to normal, and 
> remained normal.
> This behavior happened again today.
> 
> Up to the first occurrence a few days ago my Mac has been rock steady.
> 
> Does anyone have any ideas of what might be going on?
> Do heat sensors fail?

Dust build up, particularly hot days, failing fans, there's a long line of 
possible failures before temp sensors go wonky; they're pretty simple and 
stable things.

My first step would be to open it up and blow it out with canned air. (outside! 
You would be amazed at the havok a charging dust rhino can wreak 8-)

Then I'd make sure both fans were in fact turning.

Look at Activity monitor when it's started up and cranking along. If something 
is causing the CPU to spike, maybe there's something going on software-wise to 
cause this.

-- 
Bruce Johnson

"Wherever you go, there you are" B. Banzai,  PhD

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