Killkrt
Level 1 (0 points)

Q: Fan spins slow even with high CPUs temperature

Hi,

 

Today I noticed a strange thing. I was making a rendering with Blender (a 3D graphical program) I was expecting my iMac fans getting to make some noise as usually when I make such heavy CPU stuff, but even if the average CPU temperature was about 75°C/80°C (reported by iStat 5) the CPU fan was spinning at 950RPM as usually! I touched my iMac and it was clearly hot than usually. When I stopped my render, the average temperature was around 80°C/85°C and fan was spinning at 1100RPM (too slow!!!). I restart my iMac to check if the fan gets the right speed, but nothing happen, it was at about 1000RPM.

 

I could fix this problem? It seems to be happen recently, I am quite sure that two weeks ago the fan was spinning right!

 

Thank you.

 

My configuration:

iMac 27" Mid 2011, Core i7, 12GByte RAM, Samsung 840 Pro SSD installed manually (more than one year ago).

OS X: 10.10.1

Logic Pro X, OS X Yosemite (10.10)

Posted on Jan 25, 2015 10:14 AM

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Killkrt

Q: Fan spins slow even with high CPUs temperature

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  • by Allan Jones,

    Allan Jones Allan Jones Jan 25, 2015 10:26 AM in response to Killkrt
    Level 8 (35,321 points)
    iPad
    Jan 25, 2015 10:26 AM in response to Killkrt

    Unneeded third-party utilities--anti-virus, so-called "cleaning/optimization/tunes up" apps, and some backup software can cause such problems. Are you running any of that stuff? This Apple atricle is useful for finding things that run up your temps:

     

    Runaway applications can shorten battery runtime, affect performance, and increase heat and fan activity - Apple Support

     

    As you are running OS10.10, there is a change in the important Step 3, setting Activity Monitor (AM) to find the really bad actors. In Step 3, the way you get 10.9 and 10.10 to show "All Processes" has been moved to AM's "View" menu:

     

    AM_Mav_select all processes.png

    Also, the test will not reveal much if you run it immediately after a restart. Use the computer normally for about a day and then run the rest. It also helps to quit any applications you launched.

     

    You will be looking for any process that is using more than about 10 percent of the resources while the computer is basically at idle (no user-launched apps running).

     

    Adware can also affect temps. This Apple article talks about adware and how to evict it:

     

    Runaway applications can shorten battery runtime, affect performance, and increase heat and fan activity - Apple Support

  • by Killkrt,

    Killkrt Killkrt Jan 25, 2015 10:36 AM in response to Allan Jones
    Level 1 (0 points)
    Jan 25, 2015 10:36 AM in response to Allan Jones

    Thank you for the answer, but my problem is not finding which program is overloading my CPU (I know it's Blender since I'm making a 3D graphic animation render). The problem is that my system temperature goes very high and system fans seems to spin at normal speed (or a little faster). I can tell you since they are very quite and iStat 5 is reporting me.

     

    I'm making a test right now (after a reset of NVRAM, just in case...), here my complete sensors dump:

    Screen Shot 2015-01-25 at 19.35.41.png

     

    As you can see the temperature is quite high, but the fan spins very slow!