5k iMac Freezing and Restarting

[the jedi path]

Hi, I searched but the ones I saw, they would get a message saying "your computer has restarted because of a problem". However, I am not getting that message at all. It just freezes, then after a few seconds the screen turns off, then restarts up and when I sign in everything I was working on is there. It's like it doesn't know it just restarted.

My 2014 5k iMac used to randomly restart overnight sometimes, and would give me that message, but this one isn't doing that. It's usually randomly when in use. I did instal new RAM. When I had the OG RAM it restarted overnight like the 2014 but never froze like this is. This is the RAM i bought. I did a check, and it never finds a problem with the RAM. So my thought is to return it. Any other help would be appreciated so much.

http://amzn.com/B016OZKL3A

specs:
late 2015 27in iMac,
4 GHz Intel Core i7
AMD Radeon R9 M395X 4096 MB
32 GB 1867 MHz DDR3

 

[squidward]

I had that issue with one of my iMacs, late 2013 i7/780m/32gbRAM/3TBFUS. The ram was 3rd party. I used Apple Diagnostics and it showed the issue to be caused by Ram. Since I had AppleCare I brought it to the Genius Bar and they said it was the LogicBoard after running stress tests overnight. After getting it back from a logicboard replacement under warranty, the issues still persisted. I diagnosed it again and it stated it was RAM. I then started testing sticks of ram individually and found the stick of ram that was the culprit. In my case, the logicboard may have become defective and may have damaged the RAM. Or maybe the Ram was the issue the whole time and Apple replaced the logic board for nothing. Either way, I RMA'd the RAM and had no issues with the new set.

It was definitely strange that out of nowhere the iMac shut off and rebooted. In the beginning it tried reinstalling it, running it factory fresh and issues still persisted. I'm glad that it stopped after I replaced the RAM. Not sure why Apple did not catch that. The RAM I used was 32GB of Corsair Vengeance.

Apple Diagnostics: https://support.apple.com/en-us/HT202731

 

[the jedi path]

I ran that and it said it didn't find any problems. I'm going to try again in the morning.

Really sucks because the return policy says I lose 15% restocking fee if they don't find a problem (why would THEY want to?) and then I'd have to wait until mid jan to go ahead and get some from OWC. Wish I had done that to begin with now.

 

[squidward]

Bummer. Did you reset smc? https://support.apple.com/en-us/HT201295 after installing the ram? Try resetting the NRVRam along with the smc https://support.apple.com/en-us/HT204063

I would also try reinstalling OS X. if possible, take it to the AppleStore

 

[Fishrrman]

Have you tried re-installing the ORIGINAL RAM, and then running it that way for a few days?

Or -- if you added RAM, removing the new RAM, leaving the original RAM "as shipped from the factory" ?

 

[the jedi path]

I'm going to try to reset the SMC in the morning. I have not tried re-installing the OG RAM, since it happens so randomly it might take a day or two to happen again. It happens about once or twice a week for the past 3 weeks I've installed it. Happened right away after rebooting the computer after instal, then a couple of days later. I'm running low on days left in my return policy lol.

I completely replaced RAM though 8gb x 4. So I would have to go back to 4gb x2 setup.

 

[squidward]

Install the original ram and reset the smc after. Let it run for a few days along try and run apple diagnostics and see if you have persistent issues.

 

[maflynn]

I did instal new RAM.

IF the computer was working fine, then you make a change, such as upgrade the ram, and now it freezes. The odds are pretty good, that its ram. As squidward mentioned pull the ram and put the original ram to see if it returns to stability.