How do I downgrade from High Sierra to Sierra?

[kebabman]

Hi there

I'm running the Live 9 suite on a 2012 MBP under Sierra and it works well.

I recently bought a 2011 MBP that I want to use as a backup machine and hopefully link to my 2012 MBP. The 2011 machine originally had Sierra on it. A computer shop put an SSD in it for me but they have also changed it to High Sierra. They have also used a Time Machine back from an external HD which I made from the 2012 machine. When I now run the 2011 machine I get really loud fan noise which sounds like there's a 747 in there! The noise quietens down after a while but then starts up again as soon as I try and do anything such as open Live.

How do I roll the 2011 MBP back to Sierra? Can I use my main Sierra 2012 Time Machine external backup? Can I use this to put on to the machine? Do I need to install Sierra first? Where do I get it from?

This is driving me up the wall so any help will be very appreciated!

Thanks

[ecuk]

It the 2011 MBP did indeed come with Sierra you might be able to get away with a ‘recovery’ of macOS:
https://support.apple.com/en-us/HT204904

To restore both macOS and your files from the Time Machine backup onto the computer which you want to downgrade should also work:
https://support.apple.com/en-us/HT203981

[kebabman]

Thanks for getting back to me.

Yes I was able to use my TM drive which has put it back to Sierra. It took 7 hours to load on!

now I've still got the fan noise kicking in . I thought this was as a result of upgrading to High Sierra but it seems it's down to something else. Would having an SSD installed cause this I wonder?

Many thanks

[ecuk]

I cannot see how an SSD would cause the fan to kick in, but there are rather a lot of reasons why that might be happening. There are plenty of threads here in the forum about fan noise, especially on more recent Macs. You might want to look at those for ideas. Sorry, but I have never really looked into it because I have never experienced the problems which some others seem to suffer with their fans.

Good luck, though, and if you do find what is happening, please report back here so that others can learn.

[kebabman]

Hi there

Thanks for the reply. Yes it does indeed seem unlikely that an SSD should cause fan noise. I'll have a look at threads and report back when sorted.

Many thanks for your help