

Resetting its SMC is necessary to restore normal fan control. This affects the latest 2018 model with a T2 chip, when the Mac is connected to mains power at about the same time that its Power button is pressed to start it up. There is currently one rare set of circumstances in which an apparent firmware bug can cause a MacBook Pro to start up with its fans stuck running at full blast. If your fans come on full blast during startup, and don’t settle down, check systematically through these causes to discover what is wrong. Careful cleaning is vital to ensure effective cooling from the fans.


When a kernel panic or other system failure is so severe that the normal control system stops working.When that Mac is in Target disk mode, in which the normal control system may be unavailable in some models.

These include when the thermal control system is unavailable to slow its fans down, and are typically: There are circumstances in which your Mac’s fans may well be intended to run at their maximum. It’s the control system which slows them down from that, so long as your Mac stays cool, and the system is functioning normally. Macs are engineered for self-preservation: by default, their cooling fans are set to be full on, blasting away at maximum revs, to prevent your CPU, chipsets, and SSDs from overheating to death.
