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Model A1312 / Mid 2011 / 2.7 & 3.1 GHz Core i5 or 3.4 GHz Core i7 Processor, ID iMac12,2

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Replace 1T HD by a 4 T SSHD, lost Fan & SSD

From Switzerland ;)

Found initially this website of great help. Anyway I did this:

"switched the HDD of my 1Tb Fusion drive by a 4Tb SSHD Seagate (same brand, 7200 rpm)"

I did not forget to put any screw back and there was no sensor on the HDD. I followed IFixit instructions but since...

- had to install everything in the 4Tb

- fan is geting crazy

- the 128 SSD disappeared (even with a command line)

I know that I did everything right but by now I am lost. Where to look for? What am I looking for?

I guess that I should find my SSD first but please without opening the Imac again ;)

Thanks in advance for your help


Answer this question I have this problem too

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2 Answers

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If I'm understanding what you're saying here, you're talking about the Apple SSD which you had in the system with the original HD.

The two drives (SSD & HD) were bonded together into a Fusion drive. What you failed to do is break the Fusion back to the discrete drives (SSD & HD) before replacing the HD with the new 4 TB drive in.

So, you'll need to reconnect the 1 TB drive back to your system which you can do externally if you have a Thunderbolt case to hold it or you'll need to put it back in break the Fusion drive.

Even still you'll need the OWC adapter for the new drive.

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Sounds like the drive you got does not have the needed firmware to support the way Apple is accessing the internal thermal sensor. Sadly, you'll need this OWC kit: OWC In-line Digital Thermal Sensor for Hard Drive Upgrade for 27" iMacs 2012 and Later. That is the best way to correct the fan issue.

As far as the SSD are you speaking about the Apple SSD drive or the SSD part of the SSHD?

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I meant the initial SSD associated to my 1Tb Seagate I replaced without taking instructions from this website. I know that the SSHD has a tiny SSD associated to it. I can open again this Imac but I want to do it right, with your answers. How can it be possible that I do not see the 128 SSD (most likely) that is into it. I used both disk utlity and the terminal.

Add. info would help

Thanks in advance



any help please? I do not see my SSD apple blade that was part of my fusion drive. I see the novel HD with the fan going crazy but that's all.



Sorry I mis-typed its a 2.5" SSD unit thats tucked under the main logic board (where Apple placed theirs). Here's the IFIXIT guide on how they place theirs: Installing iMac Intel 27" EMC 2429 Dual Hard Drive Kit. But I think were getting lost here on the SSD problem (if you have a Fusion drive setup).


For now you should contact Seagate to verify if the drive you got is compatible with the '11 or newer systems. If not you'll need the OWC cable. If it's one of the newer drives that is supported then you have to figure out what you did that messed you up.


As to the Apple SSD not showing up. You can also mount the old HD in an external case to cleanly break the fusion set. At that point it should be visible under Disk Utility. Again, we are not talking about the SSD which is part of the Seagate SSHD! This SSD is not accessible via Disk Utility the drive handles it directly (SSD cache).


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geoffrey will be eternally grateful.
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