iMac 5K doesn't wake up

[Chrysaor]

Recently got an iMac (Retina 5K, 27-inch, Late 2015 with SSD and M390) and it doesn't wake up from sleep if it's sleeping overnight. Just shows a black screen, no backlight. Have to hold power button or unplug to boot it back up.

This is on Sierra 10.12.4. Anyone else having this issue?

 

[Lunder89]

Have you tried reinstalling macOS?
You can do this without removing your files, simply by running the installer from the Mac App Store.

But make sure to have a backup, just in case.

I have a similar model (iMac 5K, late 2015, 16 GB Ram, 512 GB SSD, M390), I have not experinced this

 

[Strider64]

I first would check your settings in system preferences -> energy saver for one, you might simply have a box check that shouldn't be.

 

[Fishrrman]

Strider makes a good point above. Some experimentation is needed.

What follows isn't "a solution", but...
... since the iMac has an SSD (which doesn't need to spin down or spin up), have you thought about DISABLING "computer sleep" entirely, and just putting the display to sleep at night?

Technically, the iMac will still be "awake", but just idling with a dark display -- not really that much removed from "sleep". Fans off (or at lowest speed), CPU and GPU idle, SSD idle, screen dark.

Another thought:
If you don't keep a lot of important stuff open at night (during sleep), why not just shut it down completely? It should boot back up in seconds with an SSD in the morning.

 

[coreyk]

I have a similar model and started experiencing this same issue when I updated to 10.12.4. I have an external 4k display attached to my iMac, and the external display would turn on but the iMac display itself would remain turned off. I could also use Screen Sharing from my MBP to connect to the iMac, which had woken up even though the iMac display remained off. I tried updating to 10.12.5 beta 2 but was still having the same issue, so I ended up restoring from my 10.12.3 clone that I made prior to the update, and the issue has since gone away.

 

[ZipZap]

This problem has, in the past, been caused by improper memory chipsets. For example, I added 16Gig of memory chips from Amazon to my 8 gig and while ago. I forget the brand but it was a pretty common one. Immediately, the wake issues started. I remove the chips, the wake worked fine. I tried the OWC chips instead and they worked fine.

 

[Chrysaor]

Looks like this is related to external monitors. If I leave any attached, it doesn't wake up.

 

[Don farrow]

Recently got an iMac (Retina 5K, 27-inch, Late 2015 with SSD and M390) and it doesn't wake up from sleep if it's sleeping overnight. Just shows a black screen, no backlight. Have to hold power button or unplug to boot it back up.

This is on Sierra 10.12.4. Anyone else having this issue?

Hi I have the same problem with my 2015 iMac, It happens about once every few months . I took it to the Apple Store and the Tech felt that it was a software problem and they reinstalled Sierra .