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marcz2007 Author

Level 1

8 points

Booting from external hard drive (Catalina to Mojave) issues when installing the old OS

I followed the steps here to create a bootable installation drive of Mojave https://support.apple.com/en-us/HT201372.

I am now able to get to the install Mojave screen where I am to wait for it to install. When it gets to about 1 minute to go, the laptop turns off, followed by the laptop turning on a black screen, the apple symbol comes up and just as it starts to load, the fan gets very load and the mac book shuts off completely. I then can only stop it from restarting and turning itself off endlessly by holding options and going back to the original hard drive. Very weird stuff - any ideas what's happening and how to fix it?

https://youtu.be/yol6Z8eIVaw

MacBook Pro 13”, macOS 10.15

Posted on Sep 22, 2020 4:30 PM

Top-ranking reply

mattymusicman

Level 1

131 points

Posted on Sep 23, 2020 2:30 AM

Try this before installing and then try again.

https://support.apple.com/en-gb/HT204063

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Booting from external hard drive (Catalina to Mojave) issues when installing the old OS

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