To troubleshoot the noisy fans, I opened Activity Monitor and sorted by the column labeled '% CPU' to identify any runaway applications, which can shorten battery runtime, affect performance, and increase heat and fan activity, as documented in Apple knowledge base article TS1473. On a MacBook or MacBook Pro, the heat vents are.

The fans increase in speed as more CPU cycles are used and when the temperature rises. On a desktop model, the vents are on the back, near the top of the case. Point of order: According to a Genius at my local Apple Store, the fans in all MacBooks run any time that it is powered up, but at a very low (and quiet) speed. Needless to say, excessive fan noise is extremely distracting and it got to the point where I couldn't hear the TV over the blaring fans in my MacBook. Now, your MacBook should restart normally if the issue was with the NVRAM/PRAM. Make sure to hold down the keys until MacBook restarts again. Almost immediately after installing 10.8.4 the fans in my rMBP would run at almost top speed every waking minute. Hunter Exeter LED 54 Ceiling Fan Brushed Nickel Finish Reversible Fan Blades: Light Grey Oak & Grey Walnut LED Bulbs Included Remote ControlWhisperWind. To get going, hold down Command, Option (Alt), P, and R, keys at once and turn on the device.

Until shortly after the time the OS X 10.8.4 update came out, that is. I use a MacBook Pro Retina 13-inch as my primary Mac and love it. Apple's largest laptop adds Touch Bar support for serious design apps

How to turn on macbook pro fan