Ultra Fit USB 3.0: Excessive Heat

SDCZ43-064G-G46 / SDCZ43-032G-G46 / SDCZ43-016G-G46

I bought the 64GB Ultra Fit to use as extra storage for my Chromebook. After leaving the Ultra Fit in either the USB 2.0 or 3.0 slots for a mere 5 minutes it gets considerably hot. Even AFTER ejecting the drive and leaving it in it is still getting hot. In the 3.0 slot it gets so hot you don’t want to hold it.

I’m wondering if this is due to the LED in the case that is constantly (24/7) blinking and drawing power? Maybe this was designed to only blink when read/write???

Anyone else having this issue or found a fix??? I’m concerned it’s going to damage my chromebook and/or Ultra Fit.

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I’m concerned it’s going to damage my chromebook and/or Ultra Fit.

Me too.  Don’t use it.  Where did you buy it?  Can you return it to the seller?  If not return it to SanDisk.


as far as i could research the heating case for the ultra fit i found out that its becoming so hot because of the small size of the drive and that its not plastic.

You can ask sandisk what you can do to prevent this but as far as i know the drive is tested and its becoming slightly hotter that other usb drives but not so hot to damage the host or the drive itself.


I found this same problem. And the main reason is that it poorly designed when compared with Cruzer Fit.

If you look closely Cruzer has 6 vents/cutouts in its sheet-metal. So it provides a better heat dissipation. Whereas Ultra Fit has none.

Now it is up to SanDisk folks if they want to fix this mistake.

Please see this link below for the image for such vents/cutouts. There are 2 on each side of the sheet-metal.



5 minutes is way too short to get those kind of temperature. 99% chance that it’s a hardware issue and that’s defective. I’d check the warranty on it as well.

the level of overheat is ridiculous! this is a design issue for the ultra fit not a isolated heating problem with some units only.

Sandisk guys! Please respond with a satisfactory solution!


In my computer’s USB3, my receivers’ (One Onkyo and the other a Denon) and my samsung Bluray I have noticed heat issues…

This concerns me… My hope was to leave in a receiver for extended times to access my music but now think i cannot. Should I return to Amazon? just got it Monday…

Bought three of these Sandisk Cruzer Fit 64GB USB3.0 drives recently and was horrified to see how hot they became when plugged into a USB3.0 socket - the metal parts of the stick were VERY hot after a few minutes operation. When I pulled one of these sticks out - my finger tip felt like it had touched the metal surface of a boiling kettle !!

Amazon reviews mentioning the temperature issue have met with a response from Sandisk representatives suggesting users wait at least 30 seconds before attempting to remove the stick - that is an admission of guilt in my book !!

I think these sticks really do have the potential to damage any socket they are plugged into, and there have been reports of plastics blistering on USB Hubs - I can quite believe it !

Furthermore, when I copied data from a nearly full Sandisk Cruzer Fit USB2.0 64GB stick to this new 64GB USB3.0 stick - there was not enough space !!! I then realised the newer 64GB USB3.0 sticks give you nearly 2GB LESS than the older 64GB USB2.0 sticks !!!

Using exFAT …

The 64GB Cruzer Fit USB2.0 reports Capacity as 64,012,943,360 bytes
The 64GB Cruzer Fit USB3.0 reports Capacity as 62,171,119,616 bytes

With FAT32 the capacity points are slightly different BUT the discrepancy remains !!

How can Sandisk get away with this - even allowing for the industry norm of dividing by 1000 (and not the correct 1024) to convert from bytes, it’s not even 64000 !!!

So, not only is the USB3.0 version capable of damaging the host machine by the temperatures it can reach BUT you also get shortchanged !


I know this is a rather old thread, but I wanted to post my experience with this device too, as it is a little different from yours (and nearly everyone).

I also noticed right after I plugged the flash drive (Ultra Fit 3.0 - 32 GB) for the first time that it got insanely hot, even after transfering files from or to the device and having it ejected. This happened in every port in my desktop computer, 2.0 and 3.0. However, I brought the flash drive to work this morning and transfered over 25 GB to my work desktop (2.0 ports only). It took about 8 minutes to do it and it didn’t even get a little warm, nothing, which suggests that the problem has something to do with the ports the flash drive is connected to, and not only the the drive itself.

Does you drive get hot everytime or it depends on which port it’s connected to?

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I’ve tried different Macs (not tried a PC yet) and different USB3.0 hubs (non powered) and it still gets RED hot.

So Hot, I’ve stopped using it.

I just purchased a 128GB Ultra Fit and it overheats and disconnects when used with a HooToo USB 3.0 hub.

So I tried it with a USB 3.0 extension cable and it also gets too hot to touch, but I don’t think my transfer went long enough to have it disconnect. I’m going to try it with my laptop’s port after it cools down.

It’s pretty ridiculous this product is being sold with this problem.

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Reading and Writing to the Ultra Fit on my Acer laptop didn’t have any disconnects, but the metal part did get really hot.

Maybe the USB hub is providing TOO much power?

Since I bought this mostly for my laptop I won’t be returning it since it doesn’t seem to be affected by the disconnection problems.

I bought the SanDisk USB OTG 64GB thumbdrive, it feels hot at the USB connector, but not as hot as Verbatim 64GB Thumbdrive,

The Verbatim branded thumbdrive get really hot(whole body is aluminium) even if plugged into smartphone after prolonged use.

I guess it’s pretty normal for small thumbdrive gets hot, because of smaller heat dissipating area.

I installed a live Linux distro (Knoppix) on those. It is the first time in ten years that a USB drive kills two of my computers. Not the same flash drive, but two units of the same Ultra Fit 3.0 model (32 GB). Not buying again.

Killed the computer? Or is the USB drive is dead? These are retail drives not really designed to have an OS running from and from your other posts you state the computers are for research purposes. Depending on the workload you ahve running on these machines (data logging especially) you may simply be wearing the drives out. 

Depending on the workload you ahve running on these machines (data logging especially) you may simply be wearing the drives out. 

Especially if the drives are formatted as ext3, ext4 or ntfs.

I never heard of flash drives “killing” a PC. There might be a fatal short in the USB port you should check out. For daily use, use a total in-RAM OS like Porteus or Puppy which are specifically designed to minimize USB access and markedly extend the life of flash drives. You can install Mint or Fedora or Ubuntu but I’d limit their use on flash drives to just occasional although this flash wear-and-tear issue is almost arbitrary since memory has improved such that flash lifetimes and incidents of developing corrupted cells is measured in years with “normal” daily use. Only real-world feedback on this can tell the story.

Jim in NYC


I have just bought the 32 gb Ultra fit

And came to this forum by searching ultrafit exesive heat after transfering 5 1,5 gb files first through a usb port, then through a USB 3 hub. 

I think it is too hot indeed

And now that I have read all I really want to ask you if it could damage my compute r (???)

Maybe I should just return it

BUT It is really not comfortable for me as I bought it on a trip

I hope it can get fixed or changed

Thanks everybody


I have to say it clear It is not just a little warmer

it is VERY VERY hot

If it is in a USB hub I don’t see how it could damage your computer.  Can we assume when you’re not copying large files to it it runs cooler?

I can concur. My 128Gb Ultra Fit runs too hot as well. To the point where it begins to disconnect and reconnect constantly. The only solution is to cool the drive down and resume operations. However it only takes around 5 minutes of copying before it begins to exhibit problems.

I’ve tried blowing cool air regularly into my USB hub and it appears to remove the disconnect issue, which clearly shows that this is a heat issue.

I’ve tried the drive in both a USB hub and directly on the ports on my motherboard. They both cause it to fail eventually.

Not good Sandisk. Perhaps I got a faulty drive - I hope so - otherwise that’s just poor design and testing.