MicroSD card randomly unmounts itself

I had similar problem, try this:

go to "device manager", right click the drive under "disk drives" (not the disk controller where the code 43 error shows), click properties, click "policy", the second tab on top, then you wanna select the lower option "better performance". Save your changes. 

Alas, this makes no difference. The beast still disappears entirely (from Explorer) after the Surface has had a long sleep. It's not a physical dismount; the card is secure enough. And it's only been the 128GB card, the previous 64GB munchkin was fine.

I notice the drivers (for the "disk" and the SD controller ) are dated 2006, although the version numbers indicate an updating for Windows 8.1 (6.3.9600.xx... ), so perhaps they're not equipped to deal with such an enormous endowment? I can only hope that the Win 10 upgrade around the corner might fix the issue.

Rob

I've been using a 64 GB SanDisk on my Surface 3 since launch with no problems. I also use a 32 GB SanDisk on my HP Stream and have never had any problems. They seem pretty reliable.

I am also having a problem with the card unmounting itself randomly as well as after sleep.  I've tried numerous tips people are talking about for this problem, but none of them worked.

I initially had a 64GB card (Samsung), which worked fine; on upgrading to a Samsung 128GB card, I'm now encountering this non-appearance after sleep. It looks like a genuine Samsung, and Amazon had it down as:

Samsung Memory 128 GB EVO MicroSDHC UHS-I Grade 1 Class 10

but still with the disappearing. The Properties just has it as Generic, however, and under Manufacturer in the details tab it says "(Standard Disk Drives)". When it's working, mind, it's perfectly okay; I don't believe the card is at fault.  

I'd like to try some of these "numerous tips", but can't seem to find anything that would prevent it happening; thought it might be a Power Management thing, but it seems not. I'm hoping (faintly) that the Win 10 driver might be a bit more reliable.

Rob

Thanks everyone! I ended up ordering a Sandisk Ultra 128GB (48mb/s) from Amazon (UK). It was a wee bit cheaper than the Samsung equivalent :)

Rob - your situation sounds exactly like mine. When my Laxer was working, it was great. And I too hope Windows 10 makes things more straightforward.

As for the 'tips' I tried - probably nothing you haven't encountered. I read postings on this site, as well as a couple of other similar ones. I tried: reformatting at NTFS; full-reformatting at (original) exFAT (for returning the card, took ages!); changing the Power Management policy setting as you said; sticking a layer of sellotape! But nothing worked.

So fingers and whiskers crossed for my new card. I will probably report what happened, so that people who will have the same problem in future can add it to their information gathering exercise.

Cheers

Snow Cat

So fingers and whiskers crossed for my new card. I will probably report what happened, so that people who will have the same problem in future can add it to their information gathering exercise.

Ah, may the power of your whiskers triumph!

I wish these cards were clamped more tightly, as they are in phones; this one is going nowhere, and I'd glue it in if I thought it would help. I was thinking of getting one for the new 640XL, but maybe I'll check on that forum, see if the phones have a happier experience of these more generous storage solutions.

As for the Surface, I did learn that getting Device Manager to check for hardware changes can rediscover the card, which is at least quicker than rebooting or re-inserting (way too fiddly).

Still, only a few days (probably) until Windows 10 kicks off for Insiders, so I'll be monitoring system behaviour in general for a wee while. Eyes, teeth and ears crossed.

Best of luck,

Rob