Slow RPMs for a Fan on a MacBook

Apple has a justly lauded reputation for industrial design, and its MacBook line -- both the MacBook Pro and MacBook Air -- are valuable tools for creative professionals. While their designs are robust and feature-rich, they still run into the same thermodynamics issues that other computers do. A CPU is a small inductive heater that happens to produce useful computation as a side effect. Every Mac made in the last decade uses Intel processors and needs a functioning heat sink and fan combination.

Overheating Problems

Depending on what year it was released in (2008 to 2010 seems to be the primary culprit), the batch of Macs it was made in and some software settings, early MacBook Airs and contemporary MacBook Pros had a problem with overheating. The fans were set for a fairly low default RPM rate of under 2500 RPM, and machines could overheat and lock up.

Noisy Fan Problem

Apple raised the maximum RPMs on the cooling fans after 2010, either in response to the overheating complaints or the requirements of Intel's latest series of processors. The part of the computer that controls the fan speed would sometimes only find one fan speed setting, the maximum of around 6200 RPM, and would never slow down again. This can result in a lot of fan noise for the laptop.

Monitoring Temperature

If you're concerned about your CPU's temperature, there are several temperature monitoring utilities available. Your CPU comes with temperature-sensitive diodes (as do other components in the MacBook that are temperature-sensitive). Peculiarly, OS X doesn't have a built-in utility that reports these temperatures to the user. Available temperature monitoring programs include "Temperature Monitor" and "iStats4" (links in Resources). Normal operating temperatures for CPUs are 140 degrees Fahrenheit, or 60 degrees C.

Monitoring Active Processes

Your MacBook is constantly running multiple processes, and sometimes those processes hit the CPU particularly hard. You can find the Activity Monitor utility by clicking on "Applications" in the dock and then selecting "Utilities." It will bring up a list of all of the applications currently running. Clicking the "CPU" column header will sort these processes by the amount of CPU resources currently used. High CPU usage translates into higher CPU temperatures.

Resetting the System Management Controller

The System Management Controller is the piece of hardware that controls how the parts of your Mac respond to heat and other factors. If your fan is constantly running at a high speed, even when there aren't lots of processes running on the CPU, resetting the System Management Controller may be called for. Shut down the computer and plug in the power adapter. Hold down "Shift-Control-Option" while holding down the power button at the same time. Release all three keys and the power button at the same time, and then power up the machine. This may solve the problem with a fan running at high speed constantly.