Why won't my 2012 iMac won't work as a monitor with a thunderbolt cable for my 2015 MacBook?

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Why won't my 2012 iMac won't work as a monitor with a thunderbolt cable for my 2015 MacBook?

I'm trying to use my iMac (27-inch, late 2012, running Catalina version 10.15.4) as a display screen for my MacBook (retina, 13-inch, early 2015, running Catalina version 10.15.4) using a Thunderbolt cable to join the two.

Whenever I press CMD & F2 to sync up the screens the iMac screen goes black, but the MacBook screen changes its display to look like it has hooked up to the iMac (everything looks a lot smaller on the MacBook screen).

Any help would be much appreciated, thanks!

iMac 27", macOS 10.15

Posted on May 12, 2020 5:34 AM

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Answer 1

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den.thed

Level 9

78,556 points

May 12, 2020 6:54 AM in response to catmacauley

The Late 2012 iMac that you are using as a monitor can not be running Mojave or Catalina.

see > Use your iMac as a display with display mode - Apple Support

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Answer 2

catmacauley Author

Level 1

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May 12, 2020 9:37 AM in response to den.thed

Thanks for your response!

I just (backed up &) erased my iMac before seeing this comment and when trying CMD & F2 again with the new wiper iMac it did actually display it! Until I moved my macbook and accidentally shut it’s lid too far, stopping the connection.

Although now it’s doing what it did originally and just making my iMac screen go black.

Do you think I have any chance of making it work since it did that one time or not?

Thanks

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Answer 3

Jun 15, 2020 9:34 PM in response to den.thed

that is such a very annoying answer. Apple needs to do a better job of educating the customer on how long devices are compatible and how best to determine when the replacements should be brought in.

I have a late 2012 iMac with the 21” screen

A 2015 MBA, An iPhone XR , and an iPad 6th generation.

What I wanted to do was simply connect the MBA and iMac to have 2 displays: but i cant because the iMac now runs Catalina. Nor can I find the correct adapter for the iMac 2012 thunderbolt or may display adapter whatever it is. None of the five adapters I bought fit the back of the iMac

Ii wanted to try Sidecar with the iPad- no can do. not compatible

So I have four individual Apple devices that cannot network together. Very disappointing.

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Why won't my 2012 iMac won't work as a monitor with a thunderbolt cable for my 2015 MacBook?

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