Macbook Pro fan running full speed, activity monitor shows no computationally intensive applications

Trouble with fan speeds can almost always be solved by resetting the System Management Controller, or SMC.

After performing normal troubleshooting, these symptoms may indicate that an SMC reset could be necessary.

Fans

• The computer's fans run at high speed although the computer is not experiencing heavy usage and is properly ventilated.

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The procedure for laptops with removable batteries is as follows:

1. Shut down the computer.
2. Disconnect the MagSafe power adapter from the computer, if it's connected.
3. Remove the battery.
4. Press and hold the power button for 5 seconds.
5. Release the power button.
6. Reconnect the battery and MagSafe power adapter.
7. Press the power button to turn on the computer.

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In the context of the statistics shown here, the 'faults' represent 'page faults', which are actually benign and refer to an attempt to read something that was not present in memory. This is taken care of in the virtual memory system by 'paging' the requested memory into the memory map of the process. But the OS keeps track of how many of these there were. If the number is very high, it can mean that you don't have enough RAM, or that you have a large number of processes trying to use more RAM than is currently to hand.

Assertions represent something unexpected by the program, and would be indicative of some kind of problem. I would be surprised to see any of those in 'live' commercial software, though.

Things that can drain battery more than expected include:

• The Flash plugin. This is a memory hog and should die already.
• Google's Chrome browser. It has been shown that using Safari instead of Chrome can add up to an hour of usable battery life. (This is a known issue)