Most upgrades seem to relate to the 27" iMacs, which have enough room for a thermal sensor cable as sold by OWC. Unfortunately there's (as of yet) no way to upgrade the slow 5400rpm HD in a 2012 iMac.
Even after 2 years of searching (on and off) I still haven't found a way to either add a thermal sensor to an after market SSD, nor have I found a way to completely disable the thermal sensor with a hardware solution. The only possible solution so far seems to be to use a piece of software to adjust the HD-fan instead.
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@beneshelman; Do you have a link to, or maybe an explanation for us, on how you added the external sensor to solve the fans from spinning like crazy? I'm pretty confident in opening up an iMac (done it plenty of times), but adding cables that weren't there is not something I have experience with :)
Most upgrades seem to relate to the 27" iMacs, which have enough room for a thermal sensor cable as sold by OWC. Unfortunately there's (as of yet) no way to upgrade the slow 5400rpm HD in a 2012 iMac.
Even after 2 years of searching (on and off) I still haven't found a way to either add a thermal sensor to an after market SSD, nor have I found a way to completely disable the thermal sensor with a hardware solution. The only possible solution so far seems to be to use a piece of software to adjust the HD-fan instead.