TLDR : Fans randomly start spinning like crazy and calm down only if I close the lid.

Hello there !

At work, I have a MacBook Pro 15" mid-2015 (2,5GHz Intel Core i7, 16Gb 1600MHz DDR3). I have basically the same apps open all day long and it works fine with the CPU at roughly 50°C.

A few times a day, while I minded my business and doing nothing in particular, then fans start spinning very loudly (but the CPU temperature stays the same).

The first times it happened I thought there was something like the time machine working in the background but I checked and its not. Moreover, if I bear with it and don't do anything, they keep spinning like crazy for hours and never seem to calm down.

The weird part is : If I close the lid of my computer (which is plugged to another screen, so it doesn't shut down or anything), the fans calm down slowly. If I open the lid again while they're calming or when they're done, the problem doesn't come back immediately (but will eventually, a few hours later).

I've read about people having fans spinning WHEN closing the lid, but I don't know what to do about this problem in particular.

Any idea ? :D

  • Hi ! I didn't know about Apple Hardware Test thanks. I tried it but it says nothing special. I tried resetting SMC a few times and tried again today just to be sure, but problem's still there :( I opened the computed and the battery seems a bit "puffy", maybe it's just damaged. Commented Dec 1, 2020 at 8:16

2 Answers 2


You may as well ignore the fan thing unless it really bugs you. What I would do is download Macs Fan Control. Once the app is running, keep it running in the background. When the Mac fan starts up again, open the app and set the fan to a certain speed, and then reset it to automatic.

  • 1
    Thanks :) Yeah the noise it's a bit annoying to me, and even more so to the seven people sharing the room. Although, using the app you recommended allowed me to set some conditions to the fans such a temperature threshold and it worked perfectly. Commented Jul 6, 2020 at 6:08
  • @DavidCarrière Yeah. Well, hope my program suggestion helps. Commented Jul 6, 2020 at 6:11

You mention you have an external screen connected. In my experience, mixing retina and non-retina displays can cause the graphics card to work extra hard (hence why I work with my laptop screen closed).

My guess is is not the CPU that is getting hot, but the GPU. Not sure if there is an app that can display the GPU temperature to prove this theory.

  • Macs Fan Control, also mentioned in another answer here, shows the GPU temperature(s) as well if the system has a GPU.
    – Alper
    Commented Apr 24, 2022 at 7:19

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