New MBAir fan runs at high speed for no reason.

I have one of the new 2011 Airs. On occasion, I will notice the fan running at full speed even though I am not currently doing anything heavy. I assumed that I had a stuck process somewhere, but using the Top terminal command, nothing stands out. In fact, usually the machine is idling and Top itself is the only thing using cycles. Looking at iStat, the machine load is 1 or 2 percent, idle is 98 or so, the temperatures are normal with the hottest item being the CPU at about 53. And it is in a very cool room at about 72f. When the machine is hung in this mode, the fan will never drop below 6000+. It has to be a hung process somewhere, because if I reboot, the fan will slowly drop to a normal speed over a few minutes. What is puzzling me is that I see no sensor anywhere that is slowly cooling down.

I am starting to log what I start up to attempt to figure out what was running just before the fan cranks up, but so far haven't tied it to anything.

Ideas, anyone?

Sounds like you've already checked in the right places. Since you don't see any active process that's tying up the CPU I'd recommend trying an SMC Reset - and if that doesn't solve it - head to the Apple Store.

It is a bug somewhere, not a runaway app. It happens when I connect my Air to the Thunderbolt display, despite whether or not any app is running.

I connect the Air to the Thunderbolt display (Air is on, but with the cover closed), I open the hatch to get the system into full screen mode on the T-display, close the cover and shortly the fan slowly begins to climb to over 6000 rpm. It will stay there until I either unhook the big display, or reboot the system. From then on, no problem unless I unhook and rehook again.

cptkrf said:

It is a bug somewhere, not a runaway app. It happens when I connect my Air to the Thunderbolt display, despite whether or not any app is running.

I connect the Air to the Thunderbolt display (Air is on, but with the cover closed), I open the hatch to get the system into full screen mode on the T-display, close the cover and shortly the fan slowly begins to climb to over 6000 rpm. It will stay there until I either unhook the big display, or reboot the system. From then on, no problem unless I unhook and rehook again.

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Just to see if its not getting enough air in clam shell mode maybe connect your MBA to the display but keep your MBA open see if it still heats up. i know my MBP does this as well but i wouldnt think the MBA''s would.

RustProofCorn said:

Just to see if its not getting enough air in clam shell mode maybe connect your MBA to the display but keep your MBA open see if it still heats up. i know my MBP does this as well but i wouldnt think the MBA''s would.

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No. It isn't a heating problem. For one thing, it is in a constant 70 degree basement, and IStat Pro shows every sensor to be cool. And the case is room temperature cool.

That being said, when I reboot, it acts exactly like a hot spot is cooling down. After the reboot, the fan still goes to high, but slowly slows down to normal - again, just like some sensor was gradually cooling.

Now that I know what is causing it, it doesn't bother me since I can stop it. The next time I get to the big city, I will stop in and let the store look at the problem. Or if it turns out to be a firmware problem, I assume that eventually it will get fixed.