I replaced a hard drive in a 2011 iMac (Core i7), though it was a standard hard drive and didn't have a location for the S.M.A.R.T. cord. (Or at least I think that's what it was.) Since then, the internal fan has constantly been running. I don't want the fan to burn out, and it is becoming quite a distraction for the user.

I believe there is a terminal command that turns off the fan, I believe by bypassing the S.M.A.R.T. test, but the Google gods are not forthcoming with this information. Does anybody know how I can turn off the fan?

  • Is what you call „the S.M.A.R.T. cord“ a two-wire cable between the main logic board and the (former) HDD? If so the that is (was) the connection to the internal thermal sensor of the (former) HDD. It can be replaced by a discrete thermal sensor which is to be fastened on your new drive (by adhesive tape or so). You can use an optical disc drive thermal sensor cable for that, it has the same sensor. The Apple part number is 593-0493, it should be available below 10€ (or 10 US$). Jun 3, 2018 at 0:42

7 Answers 7


You should definitely try resetting the SMC, since it's a known fix for fan issues. Here are the instructions: Resetting the System Management Controller.

  • I will definitely be trying this tomorrow. I think I came across this in my research, but I don't know why I never tried it. I think I tried resetting the PRAM with no luck. Thank you
    – Jonathan
    Oct 2, 2012 at 22:39
  • It had donned on me that I had tried that over night when I first started experiencing it to no avail. I ended up nuking/paving the os (when I copied the HDD, I didn't realize there was an error and it copied as case-insensitive). When that was done I did the SMC reset trick. Not to sure the exact resolution but I believe it has been fixed. Thanks
    – Jonathan
    Oct 3, 2012 at 19:10

Macs Fan Control can set the fan of an iMac (or MacBook, or other hardware) to any speed. The coolest thing that it can also set a fan to sensor-based control depending on your new HDD by reading its S.M.A.R.T. temperature.

This free app is much better and powerful than HDD Fan Control, which is currently deprecated but still costs $35. Macs Fan Control also works under Windows in Boot Camp.

  • This worked a treat macupdate.com/app/mac/47386/macs-fan-control Changed HD to ambient and solved the problem. Thanks
    – user63338
    Nov 25, 2013 at 9:58
  • Working perfectly for an iMac i5 with a Seagate Barracuda 2TB HDD. From the developer's site: Solving iMac fan noise issue after HDD replacement. But where did you get the info that HDD Fan Control is currently deprecated? (@GeekUser).
    – brasofilo
    Feb 27, 2014 at 13:41
  • Maybe because the latest version if almost 2 years old?..
    – GeekUser
    Mar 6, 2014 at 16:28
  • It is definitely deprecated, because it doesn't support iMac models from 2012 onwards. The fan of those models isn't detected, the preference pane just shows "-1 RPM" and adjusts nothing. Glad I checked the demo before buying.
    – LukeLR
    Jan 11, 2017 at 4:10

I Just downloaded the Macs Fan Control to fix a 2010 27" iMac. I have taken my silver beast apart about 5 times, reseating the LCD temp sensor connector, reseating all connectors, SMC resets, NPRAM erases, flex capacitor reboots, and praying to Steve Jobs collective soul to get these damn fans to slow down slow enough so I can actually hear these friggin speakers.

Macs Fan Control allowed the constant rate set for my 2 trouble fans, the CPU fan and the ODD fan. I now have to monitor my temps to adjust my fan speeds, but I don't crush big math all that often. The free program beats shelling out $800 for a new logic board for a bad temp sensor.


I have tried many different apps to resolve my noisy fan issue after replacing HDD with SSD. I was able to use iStat to determine it was the CPU fan and not the SSD/HD fan. HDD Fan Control did not work nor did SSD Fan Control. I know everything was connected and in place so I know it was not a cable/sensor issue. I have been working on this for hours and finally found this website and downloaded Macs Fan Control, set them to Ambient and instantly, my CPU fan went silent. I have my sanity back. Huge thanks.

  • Why I saw this message only when I've decided to sell my iMac. I've spent whole year with terrible full speed CPU fan. Thanks you a lot!
    – Denis Nek
    Oct 26, 2015 at 6:57

I had a similar problem, but i did not solve it by shutting down the Fan. Even if that would be possible, i would not reccomend it. Instead you have two options:

  1. Install "HDD-Fan Control", which i did, a very nice Control for your iMac which costs 30,-$
  2. You could try and replace the Connector from the HD to the Mainboard. Apple uses special 6-Pin Molex-like Connector, but uses only 2 Pins which connect to the MB

I went with solution #1 because it was the easiest solution - the Cable is very hard to find.

  • You're right, I meant more along the lines of controlling it, not necessarily shutting it down. I have seen HDD Fan Control, but I was hoping for a more direct solution. This will still be my fallback however! Thank you!
    – Jonathan
    Oct 2, 2012 at 22:37

Install and use SSD Fan Control that also supports S.M.A.R.T. and it doesn't cost any money.


Short out the connector that goes to the hard drive and this will tell the fans to return to normal. It's the absence of a connection that makes the fans spin up.

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