Late 2009 iMac sleep screen issue

[MMacG1167]

I have a 27" iMac from late 2009. It has a 2.8 Ghz Intel core i7 processor, 8GB of 1067 MHz DDR3 RAM, and an ATI Radeon HD 4850 512 MB graphics card/chip. It has a 1 TB SATA HD of which about 687GB is available. The OS is High Sierra (10.13.6). I essentially leave it turned on 24/7, and for a number of months now the screen has had a habit of occasionally refusing to light back up from sleep mode when I attempt activity - you can here the hardware running and clicking when I press on the mouse or keyboard but the screen will stay dark. It usually (but not always) happens late in the evening after I have used it a few times earlier in the day and it has gone through the active/sleep cycle a few times. If I leave it for a little while and try again the screen still refuses to wake, but if I leave it till the next morning it always lights back up when commanded. If I do a force shut down and briefly unplug the iMac then the screen will almost always light up properly on restart. If I do not unplug it more often than not it will not fix the problem upon restart. Again, I cannot say there is a completely definitive or predictable pattern to when this occurs - there are periods of days where it does not seem to happen at all, and then times when it happens almost every day. Could this be a software problem? Or is it more likely to be a hardware issue?

Thanks

 

[FlorisVN]

let's start resetting smc and do nv/pram reset.

I also recommend you run a Apple hardware test, or Apple ASD hardware test.

Post results here...

 

[mikehalloran]

Although you might have a hardware issue on a 9 year old iMac, not enough free RAM will cause this. Memory leaks are a fact of life and browsers are among the many offenders. You don't say what apps you run.

Reboot daily. If you find this happening towards the end of the day, replace two of those 2G sticks with something larger. You may have another hardware problem but this is the normal culprit.

There are those who disagree but I see this a lot. Many of my customers are schools running late 2009–2011 iMacs with 8G RAM.

 

[MMacG1167]

Thanks for the responses. I reset the nv/pram and then the smc, apparently successfully each time. I then tried running the Apple hardware test. I am not very tech savvy in general, so I looked on apple support for how to do this (https://support.apple.com/en-us/HT201257). It said to shut down the computer, then restart it with the D key pressed down until the Hardware test icon appears. So I did this, but the screen remained dark from start up. I could hear all the workings of the computer going on but the screen remained dark, until finally I starting hearing the repeated warning beeps letting me know that I needed to release the key I was depressing. The screen remained dark for almost 10 minutes after startup and I then did a force shut down. I attempted the hardware test a second time with the same result. This time I left the computer running and checked it again more than two hours later, when I attempted successfully to have it wake up out of sleep mode (the screen lit up this time). So I have not been able to get the hardware test to run, and trying to results in an unresponsive, dark screen. Does this indicate anything in particular? In terms of the programs I run, I essentially only use Safari for web browsing or occasionally a word processing program, mostly Textedit. So nothing that should be demanding in terms of computing power.

Thanks