My Mac is running hot with the fan cutting in often. How can I diagnose what's wrong?

PS: Some sources mentioned Activity Monitor as a tool to diagnose this, but I couldn't find the application.

  • Can you start it using Spotlight (cmd + space)? See this Apple support page for help if you need it. – fsb Apr 2 '17 at 2:38
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    Activity Monitor is found in Macintosh HD > Applications > Utilities. – IconDaemon Apr 2 '17 at 3:09

As IconDaemon mentioned in their comment, Activity Monitor is by default located in Macintosh HD > Applications > Utilities.

However, since your question seems to really be about your Mac running hot with the fan cutting in often, and since you say you're not proficient with Mac OS - any pointers welcomed, I thought I'd suggest you try starting in Safe Mode and potentially also resetting the System Management Controller (SMC).

Boot into Safe Mode

As a troubleshooting step you can boot your Mac into Safe Mode to see if your issue persists, both during Safe Mode and afterwards when booted normally again. Follow these steps to boot your Mac into Safe Mode:

  1. Fully shut down your Mac
  2. Restart your Mac
  3. Immediately press the Shift key and keep it down
  4. Let go of the Shift key when you see the login window (NOTE: If you have FileVault enabled you may need to log in twice).
  5. Take a note of what happens (i.e. is your Mac still running hot, etc)
  6. Now exit Safe Mode to restart your Mac as normal
  7. Again, take a note of what happens (i.e. is your Mac still running hot, etc)

Once you've booted into Safe Mode, let me know how you went. However, if the issue persists (especially if it persisted during Safe Mode) you can reset the SMC to see if that resolves the issue.

Reset the SMC

Your computer's System Management Controller (SMC) is responsible for a wide range of functions, including your Mac's cooling fans, power management, battery performance, and the list goes on. The instructions for resetting your SMC depend on whether your device runs

  • from a built-in battery?
  • a removable battery?
  • off AC power (i.e. plugged into a power point)?

Since you don't actually specify your model of Mac, I will provide the steps for all three scenarios. Ensure you select the one that applies to you!

For MacBook Pros, MacBook Airs, and MacBooks where you can’t remove the battery on your own (i.e. it's a built-in battery), here’s what you do:

  1. Shut down your computer
  2. Keep the MagSafe adapter (power cable) plugged in.
  3. Press at the same time shiftoptioncontrol (on the left side of the keyboard) and the power button
  4. Let go
  5. Turn your computer back on with the power button.

For MacBook Pros, MacBooks etc that you can remove the battery from, here’s what you do:

  1. Shut down your computer
  2. Disconnect the MagSafe plug (power cable) from the computer
  3. Remove the battery
  4. Press the power button for 5 seconds and release
  5. Put the battery back in
  6. Reconnect the MagSafe cord (or power cable)
  7. Turn your computer back on with the power button

For iMacs, Mac Pros, Mac Minis, etc that only run from a power point in the wall

  1. Shut down your computer
  2. Unplug it from power
  3. Wait 15 seconds
  4. Plug the power cord back in
  5. Wait for an additional 5 seconds
  6. Press the power button to turn it back on

Once you've used the appropriate steps to reset the SMC for your model, report back on how you went.

Intel Mac temperature database

As an aside, you may be interested in the Intel Mac Temperature Database. This will give you an indication of the typical temperature ranges experienced by users of various intel Macs. The list can be filtered to suit your needs.

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  • A good answer but not to this question - your answer deals with if there is a problem with the fan but the question is how do I find if there is a problem and most likely it is software – user151019 Apr 3 '17 at 10:56
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    Yes, my answer doesn't fit so much now that the question was edited. :) Originally there were two: (1) finding Activity Monitor, and (2) the OP welcomed any pointers to resolve the issue as they aren't proficient with macOS. The original question didn't actually mention diagnosing the problem. Regardless, resetting the SMC is useful both in terms of the fan and also high CPU usage (especially in instances where there is no apparent need for it). Regardless, I've just edited my answer to suggest they try booting into Safe Mode to see if the problems still persists. Thanks for the feedback. :) – Monomeeth Apr 3 '17 at 22:17

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