Fan speed goes high while Fan Control shows 0 rpm, no hardw.replaced
My iMac Intel 21.5" EMC 2308 with original build in 2TB HDD and 8GB RAM shows occasionally high HDD fan speed for some seconds up to an hour (or longer?) while Fan Control shows 0 rpm and the temperature ist still under 50° C. SMC and other resets didn't help.
No hardware has been replaced, only OSX to 10.9.5.
Is the HDD fan speed sensor damaged?
Andreas