Can the wireless card be upgraded in the iMac 2012

Thanks for your input. What do you mean by "don't work reliably"? It won't work at all? or it'll work but with slower speeds?

I'll let @danj explain on the blade, he knows more about trying to use the mSATA blades with adapters than I.

Thanks! While I wait for @danj to reply, I want to ask another question, If I replace the 1TB hard drive with a 512GB Sandisk SSD that I have, and don't use the thermal sensor by OWC, Will the fan run full speed? I've seen some youtube videos, and while they didn't use any thermal sensors, they report no issues with fan speeds. I'd like a second opinion on this.

Review this IFIXIT answer: Will a Samsung 850 EVO drive work in this computer? While this is a MacBook Pro Vs your iMac, the SSD support is the same across the two.

As to what we saw in our limited testing when we tested in a few MacBook Pro's there was a high error rate and file corruption when we stressed the I/O using synthetic & real file testing. I wouldn't use it even in my own system as it was such a crapshoot on when it would fail.

We only tested with one carrier and three different SSD's. The Samsung SSD 850 EVO was the better one but it to had too many errors to be reliable enough. Don't forget this is not a NVMe drive! Only a SATA (AHCI) drive. So it was not running in the faster mode the system was designed to support and Apple could alter the systems firmware in a future OS release to kill off the dual mode support the older PCIe x2 systems had. I wouldn't be surprised a lot of people will encounter issues with the new High Sierra file system.

Unlike HD's SSD's data moves are much faster so the connections and the distance of the interconnection has a bigger bearing. As an example with older SATA MacBook Pro's we often see the SATA cables degrading which create errors and can in fact kill the drive. In addition, the higher error's (CRC's) can also wear the SSD so the lifespan of the drive won't be as long.

Either use the real Apple SSD or OWC's thats the only answer presently. OWC does not currently support using their blade SSD in the newer iMac's.

Thanks @danj for your kind assistance. I bought a genuine Apple SSD (MZ-DPC2560/0A2) that came from a Macbook Pro 2012 according to the seller. Will that work in my iMac 2012?