iMac 24inch alu shutting down for no reasons

[virusbeatbox]

Hi!

I've been having this problem with my 3.5 year old 24-inch aluminum 3.06ghz iMac quite some time now. I have asked this question at 4-5 other Mac/Apple specialized websites but NONE has ever given me a solution or even an answer of what the problem might be.

The problem is that, when my iMac is booted up for 5-10mins without performing heavy duty, it shuts itself down without any warning or message. It looks like the power cable gets pulled out. I've done a million things already, I'll list them here for the easy of reading:

- Formatted HDD
- Full new install of OS X
- Bought new RAM and replaced them with the old ones
- PRAM, NVRAM,...
- Ran Apple Hardware Test many times for hours without any message saying there is a hardware problem
- Tested the PSU with a multimeter but everything OK

Noticed that the LED diagnostic leds were burning so I searched the meaning of each light. At iFixit I found out that the fourth led indicates that there is a heat issue. I used compressed air to dust out the iMac and the fans but there wasn'te even any small dust particle in there. I also installed Hardware Monitor to see the temperatures and i saw the Heatsink and GPU was around 70°C before it shutter down.

So I bought cooling paste and applied on the CPU as well as on the GPU. Then i booted up, saw the 4 leds still were burning. I ran Hardware Monitor to see what the temperature was. All was under or around 20° Celcius and the Heatsink was around 50° Celcius (what i think is a great improvement since previous).
Still it fell off just like before.

I really don't have any clue what the problem could be. Could someone please give me some advice to try things? Thanks in advance!!

[RedCroissant]

Originally Posted by virusbeatbox

Hi!

I've been having this problem with my 3.5 year old 24-inch aluminum 3.06ghz iMac quite some time now. I have asked this question at 4-5 other Mac/Apple specialized websites but NONE has ever given me a solution or even an answer of what the problem might be.

The problem is that, when my iMac is booted up for 5-10mins without performing heavy duty, it shuts itself down without any warning or message. It looks like the power cable gets pulled out. I've done a million things already, I'll list them here for the easy of reading:

- Formatted HDD
- Full new install of OS X
- Bought new RAM and replaced them with the old ones
- PRAM, NVRAM,...
- Ran Apple Hardware Test many times for hours without any message saying there is a hardware problem
- Tested the PSU with a multimeter but everything OK

Noticed that the LED diagnostic leds were burning so I searched the meaning of each light. At iFixit I found out that the fourth led indicates that there is a heat issue. I used compressed air to dust out the iMac and the fans but there wasn'te even any small dust particle in there. I also installed Hardware Monitor to see the temperatures and i saw the Heatsink and GPU was around 70°C before it shutter down.

So I bought cooling paste and applied on the CPU as well as on the GPU. Then i booted up, saw the 4 leds still were burning. I ran Hardware Monitor to see what the temperature was. All was under or around 20° Celcius and the Heatsink was around 50° Celcius (what i think is a great improvement since previous).
Still it fell off just like before.

I really don't have any clue what the problem could be. Could someone please give me some advice to try things? Thanks in advance!!

This might be something that you might have tried but didn't list. Do you have the iMac plugged directly into a grounded wall outlet or is it plugged into a power strip/surge protector? Because it doesn't sound like you have any major problems and it might just be that your power source has small fluctuations that could be causing this.

[macthefork]

Could a Terminal command have been entered by someone (such as sudo shutdown -h M)

What does the Console Log show prior to it shutting down.

[virusbeatbox]

Originally Posted by RedCroissant

This might be something that you might have tried but didn't list. Do you have the iMac plugged directly into a grounded wall outlet or is it plugged into a power strip/surge protector? Because it doesn't sound like you have any major problems and it might just be that your power source has small fluctuations that could be causing this.

Yes indeed I tried this but forgot to list it. The iMac is plugged into a power strip. I tried to put it into a grounded wall outlet without result.

Could a Terminal command have been entered by someone (such as sudo shutdown -h M)

What does the Console Log show prior to it shutting down.

No one can access my computer so that kind of command could never been entered by someone.

I was able to get into the console and get the logs. You can find the logs here:
http://ppl.ug/rCZE8foLs3U/
http://ppl.ug/-GZ0ofPHR80/

Thanks already for taking a look at it!

[virusbeatbox]

Originally Posted by macthefork

Could a Terminal command have been entered by someone (such as sudo shutdown -h M)

What does the Console Log show prior to it shutting down.

You can find the logs above here.

[virusbeatbox]

Could someone please have a look at the logs? I'm really desperate in what the problem is with my mac

[HenryDJP]

Originally Posted by virusbeatbox

Could someone please have a look at the logs? I'm really desperate in what the problem is with my mac

It might cost you a little cash but it would be to your advantage to have Apple do a diagnostic since you say you've been having problems for quite some time. It might be something minor but it could be something major. At least they can tell you what's wrong and if it's cost effective to get it repaired.

[macthefork]

You probably will have to have it checked by Apple or another Authorized Repair Facility because it looks like it's likely a hardware issue, possibly related to your video card. The symptoms seem to indicate an overheat issue.

Have you run those logs by anyone over at the Apple Support Forums? Sometimes someone over there is able to answer what the shutdown codes refer to as shown in your logs.

[oprime]

To the OP, did you ever take your imac into the Apple Store for a diagnostic? If so did they find out what might be causing the shut downs.

I ask only because I am experiencing the same exact issue with my early 2009 alu Imac (I too have tried all the troubleshooting you listed with no luck either). As one poster mentioned, I have a feeling it might be an issue w/ the graphics card.

Anyways, let me know if you had any more news to report on this issue. Thanks!