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I have noticed that my MacBook Pro's fan is constantly on - it sounds like it is trying to cool down and it does this all day long.

It did not used to do before I started using an external monitor.

Any ideas?

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A little more help would be amazing. For example Year, processor, graphics, silver or black keys? If you have an older MBP (one with the silver keys 2'1 series) then their 9xxx Nvidia graphics cards are known to be faulty. Perhaps the graphics card is having to work double time to deal with the external monitor and the fact that it could be "crapping out."

Another solution is to open Activity Monitor (either through Applications -> Utilities) and look for a process that is using an abnormal amount of CPU power.

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It is the 8600gt series that has the issues. I know, I had one die on me. :( – Troggy Sep 2 '10 at 16:45
Right, sorry the 8xxx series. The new ones are rocking the 9xxx series, my bad – Braden Sep 2 '10 at 17:03
Last year, they were the 9xxx series. This years models now use the 3xx series and intel integrated. – Troggy Sep 2 '10 at 17:18
Yes, which in my mind is a horrible "upgrade." The mere fact that Intel need their graphics card in the laptop because their core iX processor is in it, disgusts me. I have vowed off purchasing a new MBP until they go back to dual AMD or dual Nvidia – Braden Sep 2 '10 at 17:21

From your description it sounds like the machine is simply working harder because it also has to deliver the image to your external monitor. You can test this hypothesis by unplugging the monitor for an hour and see if the MBP goes quiet again.

If it quiets down = problem identified, but not solved -- read on!

If not, then it may be unrelated to the external monitor. It would then be caused by more heat building up than can dissipate like it used to.

  • Perhaps the machine has become dusty? Vacuum it.
  • Perhaps a cooling system has failed? Have it serviced (or take it apart yourself if you dare).
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up vote 0 down vote accepted

Unplug external monitor and install all Apple updates (including fix for problems with external monitors and restart Mac.

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