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?