New 27" iMac RAM Problem - won't recognize more than 16GB

The Monkey said:

AppleCare thinks it's the logic board, as do I. They are sending me back to the Apple Store, which is a PITA. I would prefer a replacement but I am not over a month out from delivery.

Is a logic board replacement quick and easy?

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The logic board is... everything inside, basically. The CPU, GPU, ports etc - everything is connected to it. It's not a hard part to replace, though, once the screen is off.



You can see the bottom right piece, with the RAM slots.

The Monkey said:

.So just as I was getting annoyed, Apple comes through for me. Again. Tough to jump ship when they consistently get the job done.

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Good to hear that they did the right thing.

The Monkey said:

I went to the Apple Store again today and dealt with a good technician there. He approached the problem very methodically and did a good job keeping me informed without being condescending. End result was a determination to replace the logic board, which made sense. Now I just received a call back to tell me that they're replacing the whole machine for me. Probably makes sense for everyone from a time/cost standpoint. And I am very happy with the decision.

So just as I was getting annoyed, Apple comes through for me. Again. Tough to jump ship when they consistently get the job done.

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About time! Glad you got to deal with a competent technician -- new machine is a blessing! Enjoy

The Monkey said:

Got the machine today. Full swap out. Not a replacement of the logic board. New 'puter politely sees and reports the RAM that's in there.

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Late reply from me, but how is the new machine?!

The Monkey said:

Got the machine today. Full swap out. Not a replacement of the logic board. New 'puter politely sees and reports the RAM that's in there.

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It's smarter on Apple's part, because your problem could take a while to diagnose probably end up throwing parts at it which is a waste of time.

If I was the engineer, i'd want your unit back ASAP and run it back through the quality controls at the factory and figure out how it escaped containment with a faulty logic board of all things.

Arfdog said:

It's smarter on Apple's part, because your problem could take a while to diagnose probably end up throwing parts at it which is a waste of time.

If I was the engineer, i'd want your unit back ASAP and run it back through the quality controls at the factory and figure out how it escaped containment with a faulty logic board of all things.

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Well it's most certainly a logic board based issue, it would have been an easy fix to replace the LBU but evidently a machine replacement was more convenient for them

The Monkey said:

Thanks for the follow up, folks. Yes, it has been working just great. Love it and can't imagine having a smaller screen. My 17" monitor at work is driving me nuts. (We're in the stone ages.)

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I have 2x21's at home, and god knows what at work - good on you! enjoy the machine

larabrynn said:

That seems odd. I bought the same 16gigs of RAM and installed it with the factory 8 and have not had a single issue. I swapped locations of the factory RAM so the crucial sticks are first. Did you make sure all the sticks are seated firmly? I seem to remember that it took some effort to push them into their seat. I also did notice that the pairings are staggered, so check to see if you have matched pairs in "About This Mac" It'll show you clearly how the sticks are installed. I have read that these computers are not happy with unmatched pairs of RAM sticks. If everything looks happy, you might have some hardware issues, and despite having aftermarket RAM, Apple should take care of it.

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Quick question, How hard is the ram to install on New imacs? I read somewhere that the screens are GLUED in and the ram is NOT like the older imacs, where you can just POP in and upgrade???? I am about to order one and I thought it was big job to upgrade the ram. So I was going to order it with 16GB.. Thanks!

harleymhs said:

Quick question, How hard is the ram to install on New imacs? I read somewhere that the screens are GLUED in and the ram is NOT like the older imacs, where you can just POP in and upgrade???? I am about to order one and I thought it was big job to upgrade the ram. So I was going to order it with 16GB.. Thanks!

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On the 27" there is a trap door behind the stand for the ram. No need to unglue the screen.

harleymhs said:

Quick question, How hard is the ram to install on New imacs? I read somewhere that the screens are GLUED in and the ram is NOT like the older imacs, where you can just POP in and upgrade???? I am about to order one and I thought it was big job to upgrade the ram. So I was going to order it with 16GB.. Thanks!

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In the 2012 iMacs (both sizes) the LCD display is permanently glued to the front glass. That assembly is taped (NOT glued) to the chassis. With the proper tools, the display assembly is reported to be fairly easy to remove and replace. The double-sided tape is designed to be used once. There are repair kits that have pre-cut pieces of tape for reassembly.

The 27" iMac has a door on the back giving easy access to the memory DIMMs.

The 21.5" iMac has no access to the memory from the outside. You have to open the chassis to get to the DIMMs, which means you have to remove the taped-on display assembly and replace the tape when you reassemble. "Apple authorized" repair shops can do this (because they have official access to the tools, instructions, and replacement tape kits). Not recommended for typical users.

If this were a peecee with UEFI I'd say to try to boost the memory controller voltage, but since the EFI is locked, I can't say much else than to try a new CPU.

3rd party RAM causing logic board failure?

I have the same issue as OP. My 27" iMac (also with SSD drive) has been running with 32 GB of Crucial RAM (4x8GB) since it was new 13 months ago. I happened to notice that recently it was only recognizing 16GB. I'm not sure when it stopped seeing the other 16GB, as I don't frequently view 'About My Mac' stats.

Took it in to the Genius bar and they swapped the Crucial RAM for Apple brand. Same issue, where each port functions fine but it cannot recognize more than two sticks at once. They tell me that it needs a new logic board, and offer to replace it at a 50% discount since it's only 1 month OOW.

I haven't moved forward with the repair yet, because I'm not sure what to do. Plus I can still use the iMac, though only half of the installed RAM is functional.

My question is, could the Crucial RAM have "broken" the logic board, as this is the diagnosis I was given? They said they couldn't prove that's what happened, but it's their best, educated guess that the third party memory caused the failure.

wedontneedroads said:

I have the same issue as OP. My 27" iMac (also with SSD drive) has been running with 32 GB of Crucial RAM (4x8GB) since it was new 13 months ago. I happened to notice that recently it was only recognizing 16GB. I'm not sure when it stopped seeing the other 16GB, as I don't frequently view 'About My Mac' stats.

Took it in to the Genius bar and they swapped the Crucial RAM for Apple brand. Same issue, where each port functions fine but it cannot recognize more than two sticks at once. They tell me that it needs a new logic board, and offer to replace it at a 50% discount since it's only 1 month OOW.

I haven't moved forward with the repair yet, because I'm not sure what to do. Plus I can still use the iMac, though only half of the installed RAM is functional.

My question is, could the Crucial RAM have "broken" the logic board, as this is the diagnosis I was given? They said they couldn't prove that's what happened, but it's their best, educated guess that the third party memory caused the failure.

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You really ought to have created your own thread instead of resurrecting one that is almost one year old.

No, it is extremely unlikely that your Crucial memory caused a logic board failure. It is disappointing in the extreme that Apple (without a shred of ability to prove, diagnose, or even indicate) attempted to point the finger in this manner.

In as much as you apparently do not have AppleCare, I would be all over their 50% of cost offer. These devices are not organic, and the odds of your iMac healing itself are slim to none.

wedontneedroads said:

I have the same issue as OP. My 27" iMac (also with SSD drive) has been running with 32 GB of Crucial RAM (4x8GB) since it was new 13 months ago. I happened to notice that recently it was only recognizing 16GB. I'm not sure when it stopped seeing the other 16GB, as I don't frequently view 'About My Mac' stats.

Took it in to the Genius bar and they swapped the Crucial RAM for Apple brand. Same issue, where each port functions fine but it cannot recognize more than two sticks at once. They tell me that it needs a new logic board, and offer to replace it at a 50% discount since it's only 1 month OOW.

I haven't moved forward with the repair yet, because I'm not sure what to do. Plus I can still use the iMac, though only half of the installed RAM is functional.

My question is, could the Crucial RAM have "broken" the logic board, as this is the diagnosis I was given? They said they couldn't prove that's what happened, but it's their best, educated guess that the third party memory caused the failure.

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It's highly unlikely that swapping out the RAM damaged the motherboard. There is no way installing the incorrect RAM could damage it. At worst, the iMac simply would not boot.

Thanks, Freeman and Rambo.

Picked up the iMac with a newly installed logic board and all is well, plus an issue I was having with Airplay has also been resolved.

I'm going to stick with the Crucial RAM and hope this was just a fluke.