Weird fan speeds

[carlosbutler]

My iMac, for some time now, has had strange fan speeds. Using iStat it lets me know the exact fan speed. And generally speaking its left fan 699rpm and right fan 1440 rpm. I was doing some heavy encoding today, and it was fairly hot on the room so the fans revved up, well a fan did. The left fan didn't increase in speed although the right one went to nearly 2200rpm.

Is this a fault with the fan? Before they used to spin at the same speeds, I don't really know why it would be any different now. Is it even a problem?

 

[i7QuadCoreMania]

check your temp sensors, the fans usually rev up when the temp is high.

you either got an overheating machine or a faulty temp sensor, I doubt the fan itself is to blame unless you are a rare case.

 

[carlosbutler]

Yeah stupid mistake....

iState was showing not what I assumed was a left and right fan, but the speed of two fans; one being the CPU and one being the ODD. I realised once I installed SMC Fan Control. Pretty good app, although takes ages to power down the fans if you make them go quicker.