Note: Installing hard drives in an iMac requires disassembling the machine and should be attempted only if you have experience. If you are not confident, please refer the work to a competent technician.
Intel iMacs require the glass LCD screen to be removed.
The Non Retina pre-2012 models are feasible for a confident tinkerer. Do not use tools on the edge of the glass. If your machine requires that the glass be removed, go to an auto supply store and get a couple of the large suction cups that are use for pulling out sheet metal dents. These can be used to pull the glass without prying at the edges.
Also, when you lift the screen, you can easily rip out the various ribbon cables that attach it to the motherboard. Take it slowly and pay attention to the underside of the screen. If you have a buddy that can hold the screen tilted up on about a 25 degree angle, you may just be able to access the hard drive without removing all the cables.
The slim edge Retina iMac models after 2012 are another story. The glass and LCD are laminated to the case with glue. It requires specialized tools to disassemble, and special adhesive strips to reassemble, and the risk of expensive breakage is high. We highly recommend taking these machines to an authorized Apple repair shop if they need internal work.
Install Guides at iFixit:
iMac Intel Late 2012
iMac Intel 2013 Retina
iMac Intel 2014 and 2015 Retina
iMac Intel 21.5″ EMC 2805 Mid 2014 Note: uses 2.5 inch laptop-sized hard drive
iMac Intel 21.5″ EMC 2889 Late 2015 Note: uses 2.5 inch laptop-sized hard drive
iMac Intel 21.5″ EMC 2833 Late 2015 Retina 4K 2.5 inch drive
iMac Intel 27″ EMC 2806 and 2834 Retina 5K
iMac Intel 21.5 EMC 3069 2017 Retina 4K
Hard drive temperature sensors:
iMacs earlier than Late 2009 use an external temperature sensor that is attached to the drive. You can unpeel the adhesive holding the sensor on the drive, and reapply the sensor to the new drive in the same position.
Late 2009 /2010 iMac models use a cable from the motherboard to some pins on the drive for the temperature readings. The pinout of the cable differs between manufacturers of drives, so the safest approach is to replace your hard drive with one of the same brand. When disassembling the machine, make careful note of the thermal sensor plug’s location and orientation. You will need to reinstall it the same way. Reports are that the white dot on the connection needs to be facing up. You can check the model number of your hard drive under Apple menu > About This Mac > More Information > Hardware
If the temperature sensor is not reporting to the Mac correctly, the Mac will ramp up the fan speeds until they are running at full speed. One solution is to install some commercial software that controls the fan speed from the SMART information from the drive, rather than the temperature sensor cable http://www.hddfancontrol.com/
Some people have also reported success attaching the Late 2009 / 2010 cables to an external HD temperature sensor from an earlier model iMac or the heat sensor from an optical drive (Apple part #922-9141).
Others have reported trying one of the following:
- Replacing the temperature sensor cable with the Apple part for the correct brand of hard drive being installed
- #922-9223 for Hitachi
- #922-9224 for Seagate (note that it still may not work if the Seagate drive firmware does not report the temperature)
- #922-9225 for Western Digital
- reversing the cable leads,
- rewiring the pins
- shorting the connector by leaving it plugged in at the motherboard and using a small wire to go from one socket to the other of the jack on the drive-end of the sensor cable.
2011, 2012 and later iMacs do not use a separate temperature cable, but draw the temperature information through a connection in the SATA power connector. This apparently requires that the drive have firmware specific to Apple. The easiest solution is to purchase the hard drive fan control software http://www.hddfancontrol.com/
A free alternative is SMCFancontrol http://www.eidac.de/?cat=4 which can control the maximum speed of the fans but does not substitute the SMART temperature readings in for the hard drive sensor information.
A hardware solution is a SATA cable from OWC (around CAN$60) which inserts the temperature sensor information into the SATA power connector
- The 2012 and later iMac model of SATA Inline Digital Temperature sensor is CanadaRAM link OWCDIDIMACHDD12
- The 2011 iMac model of SATA temperature adapter is CanadaRAM link OWCDIDIMACHDD11
- The 2009/2010 model is CanadaRAM Link OWCDIDIMACHDD09
Note: Slimline Retina iMac models and the recent 21.5 inch models are glued together and we do not recommend that you attempt to install internal components unless you have experience and tools to do so.