How can I adjust my HDD fan speed on my iMac?

Manolis November 2, 2011

Can I set a maximum fan speed for my HDD fan on my iMac? I don’t want it to run at full-blast.

  1. Ted
    April 28, 2012 at 4:31 am

    I downloaded and installed HDD Fan Control a week ago, to help control one of the fans (specifically the hard drive fan) in my 2007 White iMac. For a long time, at least a year, it had run at full speed for long periods, even right after starting up. Now it's working like a charm, I give this application 5-stars for it's performance so far. While $30 seems like a lot of money compared to the cost of many applications in the iTunes Store, it's cheaper than buying a new iMac.

  2. Anonymous
    November 3, 2011 at 3:50 pm

    iMac: Fans run at full speed after computer turns on

    reset msc
    Intel-based Macs: Resetting the System Management Controller (SMC)

    in order to note damage the notebook, you won’t be able to set the minimum speed to a rate which is under Apple’s defaults. In 1400-1600 rpm range for the CPU and HD fans should keep things a lot cooler.

    The default and maximum fan speeds for the 24" ALU iMac are:

    ODD: 700/4400
    HDD: 1200/5500
    CPU: 1200/3300

    SystemLoad is a diagnostic application assisting you in the detection of cooling or power supply problems with Apple Macintosh computers.

  3. Mike
    November 3, 2011 at 6:56 am

    Even if you use a tool like smcFanControl to decrease the FAN speed within your iMac as soon as the cooling is insufficient the FAN will speed up again. It's a security mechanic built into the Mac.

    I would rather get some professional Mac support taking a look at it because most likely your FAN is full of dust.

    Another thing you have to realize is that the iMac Fans may be silent at the beginning but after ~3 years the bearing will be worn down and they start to make a distinct noice that persists even on low speed.

    • James Bruce
      November 3, 2011 at 10:28 am

      Agreed. Rather than trying to force it slow down, think about why it's running fast in the first place. It's usually either a build up of dust, or when this happened to me, I found one of the fans on the other side was dead, so the fan was trying to compensate to dissipate the extra heat. Replacing the fan will more than likely fix your problem. 

      Download the iStatPro app mentioned below and see if it indicates one of your fans is dead. I suspect so. 

  4. Jay
    November 3, 2011 at 4:20 am

    Proper Fan speed is necessary for keeping things cool and prevent over-heating.

    You can install applications to control your fan speed, mostly people use it for speeding up the fan, but you can try it to set the speed according to your requirements.
    or (not free)

    you can monitor your fan speed with istat pro: