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This fixed mine!!!

there have been quite a few reports that prntjob manager runs and causes 100% cpu usage and therefore speed up of fans, worth checking out in activity monitor if it happens again.

I had the same problem with fan always running then I read this quote and remembered that I had tried to print from my mac book a couple of days ago....cause and effect? Sure enough I went to settings > Print/fax > reset printer and the fan stopped!

Thanks so much!
 
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