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My iMac mid-2011's 500 GB hard drive recently crashed, so I went to an authorised centre to replace it. It was then replaced with a 1TB hard disk. But now I've noticed, when the computer is on for prolonged periods, there's a loud (fan) sound coming from it. Why is this happening? Is there anything I can do to fix this?
Thanks!
iMac (21.5-inch Mid 2011), OS X Yosemite (10.10.3), null
The sound you are hearing is most likely because the temperature sensor for the HDD wasn't installed correctly/at all.
You will most likely have to take the iMac back to the "authorised" centre to get it fixed properly.
However it may be a quick fix such as resetting the System Management Controller (SMC)
To reset the SMC on Intel-based Mac Computers:
The place I took it to was an authorised service centre. The temperature sensor installed incorrectly makes the fan noise? And nope, looks like resetting the SMC didn't work
It isnt the actual Temperature sensor that makes the noise, it is the sensor that tells the fans to speed up which create a loud noise.
The reason it is making the loud fan noises (high fan speeds) is because in the 2011 model iMac Apple introduced a new way of thermal management- they included custom machine specific firmware in each HDD it made for each brand of HDD it shipped.
When a user attempted an upgrade/replacement of a failed HDD with a new one, the iMac would detect that the firmware wasn't present on this new drive.
Thinking that the drive has overheated/failed the iMac goes into failsafe mode where the fans ramp up to protect its internal components from failure themselves, when in actual fact - no threat exists.
For solving this problem I can on,y recommend a return trip to the place that replaced your HDD.
But you could also fix it by manually controlling the fan speeds with utilities such as this: http://exirion.net/ssdfanctrl/
Good Luck 🙂
Sound from iMac 2011, after HDD upgrade
