I don't know why, but these days my fans for some reason run throughout the day. When the fans start spinning the computer becomes extremely laggy. I have also tried running Macs Fan Control app after reading about it, but my system still hits 80°C. At that time it also freezes for 5 seconds to 2 minutes.

So any suggestions as to why it might be happening, and how I can fix it?

Running macOS High Sierra 10.13.3
MacBook Pro (15-inch, Mid 2012)
Processor: 2.3 GHz Intel Core i7

  • 1
    When was the last time it was stripped & cleaned? – Tetsujin May 17 '18 at 19:25
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    Slowing down the fan when a computer gets hot is the opposite of what you should do. If the computer overheats it could physically damage itself permanently. The issue could be a runaway process. On my Mac often playing video or something that uses Adobe Flash will start the fan. You may want to use Activity Monitor and look for processes using lots of CPU, and if possible (like Tetsujin suggested) open it and blow out the dust with some canned air. – Steve Chambers May 17 '18 at 20:05
  • well i think i never cleaned internal section of my system. Although i regularly clean the dust on outer body. But again it's a compact device and i'm not expert enough to open it. – emulen May 17 '18 at 20:16
  • First check Activity Monitor for any process which is CPU hungry, such as kernel_task. – Pratik May 19 '18 at 12:00

So any suggestions as to why it might be happening? Is it overheating?

No, it's not overheating. It's actually attempting to prevent an overheat condition.

Your MacBook Pro is doing two things to keep the CPU/GPU within operating temperature tolerances:

When you install software to override the SMC's control of the fans (cooling), you force the system to increase the CPU allocation to prevent additional load - it will become slower.

What you should do is

  • clean the dust from the fans
  • put in new, high quality thermal paste on the CPU heat sink

There are excellent videos on how to do this procedure on YouTube

  • I am almost sure that you mean it (or think it included), but the fans are often not as much a problem compared to the grills of the heatsink. Dirty fans are easy to see but the more hidden grills are much easier clogged; and needing a blast… – LаngLаngС Nov 29 '18 at 12:13

My computer heats up massively (super hot to the touch) when plugged into power and/or plugged into external Apple display. And slows down massively (almost frozen).

The only solution that I have found, without opening the laptop, is to disconnect from display AND disconnect from power, for the laptop to cool down.

  • 1
    Please have a look at the faq to understand how AskDifferent (and other StackExchange sites) works and how it differs from the usual forum-based sites. – nohillside Mar 19 '19 at 7:03
  • Also, you may want to search for questions about kernel_task here to see whether any other question around high CPU consumption has an answer which helps you. – nohillside Mar 19 '19 at 7:04

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