Imac 21.5" mid 2011 cooling fan started and will; not stop
iMac 21.5 mid 2011 cooling fan started unexpectedly (high volume, loud noise) and has not stopped after 10+ minutes. Any ideas how to learn what is wrong?
If the SMC reset changes nothing...
Has the hard drive in your iMac been replaced? Your iMac has three cooing fans: one for the CPU, one for the optical drive, and one for the hard drive. The factory hard drive has a special sensor that controls its fan. If an aftermarket fan replaces the original drive, you must install a special cable to regain control of the hard drive fan speed.
To be sure which of the three fans is affected and whether it is a problem in the fan motor or a problem with the sensor that services the fan, run Apple Hardware Test:
How to use Apple Hardware Test on your Mac - Apple Support
Post any error codes that result here so we can identify a specific part, if possible.
