I have upgraded my iMac to a Crucial SSD but now the internal fans are noisy as the fan speed has significantly increased.
Some earlier iMacs use a separate plug-in temperature sensor cable, which attaches to a socket on the original hard disk drive (HDD) to determine the drive temperature and adjust the fan speed accordingly. Solid State Drives (SSDs) and the accompanying 2.5” to 3.5” converter bracket do not use this type of socket, meaning that the cable cannot be reattached. When you power on your iMac, the temperature will incorrectly register as much higher than normal and the fan speed will increase as a result.
*Note that any iMac that uses a ‘sticky pad’ sensor can simply be re-attached to the new SSD and fan speed is unaffected*
One of the benefits of SSDs is that they generate significantly less heat in comparison to a traditional HDD, so the increased fan speed is unnecessary. You will probably want to reduce the speed of the fan, as well as the noise, so one solution is to use a 3rd party software such as ‘SMCFanControl’. This allows the user full control of the fan speed to set it to an acceptable level.
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An alternative solution is to purchase an aftermarket sensor adapter. This type of cable converts a plug-in sensor to an adhesive one, which allows the fan speed to be automatically controlled by the iMac's System Management Controller. When using the sensor adapter, no additional software would be required.