Skip navigation

power supply fans turn on intermittently

255 Views 4 Replies Latest reply: Jan 24, 2013 6:24 PM by eholz1 RSS
eholz1 Calculating status...
Currently Being Moderated
Jan 11, 2013 7:35 AM

I have a brand new Mac Pro, power supply fans turn on intermittently, any ideas on this?

I have two g-tech drive connected and a Lacie 2tb quadra via firewire, and a g-tech raid connected via a raid controller (ATTO)


I have take system to apple store to no avail, but fans still come on, etc.





  • The hatter Level 9 Level 9 (58,575 points)
    Currently Being Moderated
    Jan 11, 2013 11:33 AM (in response to eholz1)

    Heat. What are you using to monitor? find one that is good and reliable.

    Airflow. Location and space around your Mac in your work space.

    ATTO card. It has its own fan. Does it have a utilty, thermal readings showing and fan speed?


    And testing... one thing at a time.

    Disconnect everything for testing.


    SMC Reset you already did (mention such things).

    Safe Boot.


    If you really want to, then of course take out the ATTO too while testing.


    And oh, are you running 10.8.2 or not?


    Did it ship with AHT or does it run a test from ML Recovery Mode?

  • Grant Bennet-Alder Level 8 Level 8 (48,110 points)
    Currently Being Moderated
    Jan 14, 2013 12:31 PM (in response to eholz1)

    There are several fans inside the Mac Pro. The ones you usually hear are NOT the Power Supply fans. The power supply fans are unique in that they are generally NOT controlled by software, but are controlled independently by temperature-sensing electronics inside the power supply. They seldom run at top speed unless they are clogged with dust and the power supply is overheating.


    The ones you usually hear are in several different "Zones" inside the cabinet. They are set to maximum at power-on by "watchdog" Hardware. The running software will then to reset the fans to more reasonable speeds based on measured temperatures inside the cabinet. If the software stops resetting the fans to moderate speeds, Hardware takes over and sets them to maximum in an attept to minimize heat damage.


    Fans coming on loudly may indicate excessive heat is building up in a particular Zone inside the cabinet, or that a sensor in a particular zone is not providing proper temperature measurements, or may indicate the software has crashed.

    Mac Pro (Early 2009), Mac OS X (10.6.8), & Server, PPC, & AppleTalk Printers


More Like This

  • Retrieving data ...

Bookmarked By (0)


  • This solved my question - 10 points
  • This helped me - 5 points
This site contains user submitted content, comments and opinions and is for informational purposes only. Apple disclaims any and all liability for the acts, omissions and conduct of any third parties in connection with or related to your use of the site. All postings and use of the content on this site are subject to the Apple Support Communities Terms of Use.