User profile for user: Stephen Zwerling1
Stephen Zwerling1 Author
User level: Level 1
13 points

SD Card Not Seen After Switching to External SSD Boot Drive on iMac 2015

I have migrated Monterey and all my apps and files from the fusion drive in my late 2015 27" iMac to an external SSD 2TB, the recommended LaCie Mobile SSD Secure USB-C Drive sold by Apple, following the instructions here:


Use an external SSD as your startup disk … - Apple Community. Thank you, Jack-19 for this great guide.


Everything seem to be fine, except I cannot use the built-in SD card reader. When I insert known good cards, they do not show up in finder or in Disk Utility. I can use a USB hub with an SD card reader without issue: the cards show up in Finder and the photos on them can be accessed.


I have tried shutting down and re-starting the iMac, but the problem with the internal SD card reader persists.


Is it just possible that the card reader will only work if the OS is on an internal drive? Three other external drives are present in finder, along with the SSD boot drive.


[Image Edited by Moderator to Remove Serial Number]


Earlier Mac models

Posted on Apr 26, 2023 12:17 PM

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User profile for user: D.I. Johnson
D.I. Johnson
User level: Level 7
22,373 points

Posted on Apr 26, 2023 1:12 PM

I suspect an issue with the iMac's card slot.

If you Option-click the Apple menu () and select System Information, is the Card Reader listed under Hardware?


Might it be possible that dust or other debris has found its way into the card slot?


No, it would not matter if the OS is on an external drive.


If a simple reboot of your Mac doesn’t fix things, see if the problem still happens in Safe mode (press and hold the shift key down at startup). It can take much longer to safe boot (5 min) so be patient.

How to use safe mode on your Mac - Apple Support 

Does the problem persist while in Safe mode?

Exit safe mode by restarting your Mac normally and re-evaluate the issue again.


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User profile for user: D.I. Johnson
D.I. Johnson
User level: Level 7
22,373 points

Apr 26, 2023 1:12 PM in response to Stephen Zwerling1

I suspect an issue with the iMac's card slot.

If you Option-click the Apple menu () and select System Information, is the Card Reader listed under Hardware?


Might it be possible that dust or other debris has found its way into the card slot?


No, it would not matter if the OS is on an external drive.


If a simple reboot of your Mac doesn’t fix things, see if the problem still happens in Safe mode (press and hold the shift key down at startup). It can take much longer to safe boot (5 min) so be patient.

How to use safe mode on your Mac - Apple Support 

Does the problem persist while in Safe mode?

Exit safe mode by restarting your Mac normally and re-evaluate the issue again.


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SD Card Not Seen After Switching to External SSD Boot Drive on iMac 2015

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