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My 2008 Macbook Pro Unibody 15" runs almost perfectly, but since one month or so, fans start to make noise or get activated in stupid situations where I am not doing really anything (just browsing the web or really nothing).

Sometimes the process kernel_task or activitymonitord get a lot of threads or CPU usage and consequently fan activity. I guess I installed something that somehow corrupted the system. If I boot the computer into safe mode, it does not happen! So it is clear to me that it is due to software. How could I compare system state between safe mode and normal mode so I get real clues about the cause of the problem?

I opened the Macbook and cleaned the fans, and also tried SMC and PRAM reset several times.

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up vote 0 down vote accepted

I have a Macbook Pro 13" aluminum unibody (love this thing) and the fans almost never kick on.

However, I've found that flash (i.e. youtube videos, flash advertisements) is very resource intensive and can cause the fans to kick on.

I would check to see what all is starting when you login.

Go to System Preferences -> Accounts -> Click your username on the left -> Click the Login Items tab.

The programs listed there are some of the programs that are launched on startup.

There are also other folders you can check:


Oh, and just so you know, the fans won't kick on until the last second (i.e. the computer gets scalding hot). Because of this, I have installed a fan controller that will cause the fans to kick on much sooner.

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this is a good idea. but I had a look at those places and found nothing relevant – flow May 23 '11 at 1:42
Do you know if you've installed any kernel modules at all? Also, activitymonitord is part of Activity Monitor and should only be running while you are running Activity – Bandit May 23 '11 at 2:20

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