iMacs have always had a temperature sensor for their internal components. The operating system monitors the hardware’s temperature and adjusts the internal fans to ensure optimal airflow to keep the iMac’s inner workings cool.
2009 and Earlier
Up until the late 2009 model iMacs, the hard drive had a temperature probe mounted to its cover. When you upgraded, all you needed to do was to re-attach the temperature sensor to the new storage unit’s case, and you were ready to go. The process changed with the 2009 21.5-inch and 27-inch iMacs, however. The temperature sensor is now a cable that connects directly to a set of pins on the hard drive and reads the temperature from an internal probe. It’s a better system until it comes to swapping out the hardware.
The Problem With Temperature Sensors
The problem is that no standard exists for which pins to use for the temperature sensor. In fact, each brand of drive Apple uses for late-2009 iMacs uses a different, custom cable. For the end-user, this means that if you decide to upgrade the iMac’s storage yourself, you can usually only replace it with hardware from the same manufacturer. If you use a drive from a different manufacturer, there is a good chance that the temperature sensor will not operate. In order to compensate, your iMac will set its internal fans to the maximum RPM, creating a nerve-wracking noise. Fortunately, a workaround exists. You can pick up a DIY kit for upgrading a hard drive in an iMac that includes a universal temperature sensor. This unit will work with any brand of hard drive or SSD, allowing you to choose the one that meets your needs without having to worry about runaway fans in your iMac.
How to Upgrade Your iMac’s Drive
The process of upgrading an iMac’s storage system involves accessing the iMac’s internals. Getting inside involves removing the computer’s display to gain access. Apple has changed how it attaches the display to the iMac’s chassis over the years, resulting in two different methods of removal.
2009 Through 2011 iMacs
In ‘09-‘11 iMacs, the display’s glass panel includes embedded magnets that adhere the screen to the chassis. This simple attachment method allows you to easily remove the glass using two suction cups to break the magnetic seal. After disconnecting the magnets, the only things keeping the screen attached are a few cables. Detach them to expose the inner workings of the computer, including the hard drive.
2012 and Later iMacs
In 2012, Apple changed the design of the iMac models to produce a thinner profile. Part of that design update changed how the iMac’s display was attached to the chassis. Gone are the embedded magnets in the glass; instead, the glass is now glued to the chassis. This assembly method allows for a thinner profile and a higher display quality since the display and glass panel are now fused together, resulting in a crisper display with a higher contrast ratio. The downside is that in order to remove the display, you must now break the glued seal. You also have to reglue the glass to the rest of the unit when you’re done upgrading the iMac.
Helpful Guides for Drive Replacement
Before you consider a drive replacement on a 2009 or later iMac, view the teardown guides at iFixit for your particular iMac model, as well as the install videos at Other World Computing (OWC) to see step-by-step guides to replacing your iMac’s hard drive.
SSD Replacement
Your hard drive isn’t the only DIY project you can perform once inside your iMac. You can replace the hard drive with a 2.5-inch SSD (3.5-inch to 2.5-inch drive adapter required). In 2012 and later models, you can also replace the PCIe flash storage module, though this involves almost a full disassembly of all internal components, including removing the power supply, hard drive, logic board, and speakers. By the time you’ve completed the PCIe flash storage upgrade, you would have rebuilt your iMac almost from the ground up. As you can imagine, this last upgrade isn’t for beginners, but for those who enjoy extreme Mac DIY, it may be a project for you. Be sure to review the iFixit and OWC guides mentioned above before you decide to tackle this project.
