

The only way to stop the fans from running at full speed and to return the clock speed to regular performance is to install a new battery into the MacBook Pro.

When the MacBook Pro does boot, the fans will be blasting at full speed for the entire time you are using the Mac ( resetting SMC or PRAM does not stop the fans running, only replacing the battery will).Īlso it appears that the MacBook Pro will reduce its own clock speed in this situation, thereby reducing performance.

Of course if you happen to have a replacement battery then you can typically just replace the missing battery with a working battery and the MacBook Pro will boot, but that is not always an option. It turns out that some model year MacBook Pro computers will not boot with a simple power button press after the battery has been physically removed or disconnected. In this situation, if a battery is removed or totally dead and you attempt to start the MacBook Pro, nothing happens – there is no sound, no system boot, no startup chime, nothing.
