iMac turns off suddenly

Mihalis Tsoukalos wrote:

My iMac (27'' C2D 3.06Ghz) did that earlier today.

I have Lion since Friday.

It turned out that it was my UPS - I just have to change its batteries.

Mihalis.

YES! It's been happening to me, too. But I think my problem started before I upgraded to Lion. I have a brand new iMac 1 T and it shuts down (not all the time, but more often than not) before it even gets started up. I've been through all the usual routes, Applecare, etc., and even taken it for servicing at an Apple store and the local servicer. They can't replicate or diagnose the problem. I've even had an electrician check out my outlets - no issues there.

I'm SO FRUSTRATED. Will see if Apple will replace it since they can't even diagnose the problem.

Is anyone else having this issue?

I have also had this, as well as other problems, includiong need to force shutdown following freezes iwth Lion and an eary 2008 iMac. A few days ago the computer died completely with a suspected logic board and/or video card failure.

Well folks, after wiping the disk and reinstalling Lion from scratch, my MacBook Pro FREAKING BLACK SCREENED with nothing but the OS installed!!! At this point, having experienced at least 50 of these shutdowns, black screen freezes, and automatic reboots, i called Apple support who directed me to an apple store, suspecting a hardware issue. Not having this problem before upgrading to Lion, I figured they would not find any hardware issues. At the store, the Genius Bar ran a full diagnostic and it came back clean. They then asked me to reproduce the problem, so i started opening browsers, ical, imail(which wan not even configured at this point) and anything else that would open. Youtube finally produced the death blow and zapped the screen. The response of the guy at the bar was., "Wow, that was impressive!" So, he ordered a new motherboard and RAM. Since it's return, i have not had a single issue, with the same base OS installation that i took the laptop into the Apple store with. All my apps are back on and Paralells is running my gigantic XP VM without incident. Hope this helps anyone out there seriously thinking of dicing up their Apples, like i was!

Hello all.

I thought I would chime in on this discussion. I have a 27" mid-2010 iMac that I upgraded to Lion as soon as it was released and also maxed out the RAM the same day. After doing both, my iMac began to shutdown unexpectedly. Sometimes I would get home and find it off knowing that I had left the iMac on when I left the house. But later on it began doing it while I was using it. I checked the console to see if I could track down the cause but was not able to, I didn't find anything that would indicate the cause of the shutdowns. It would also happen so randomly that I couldn't even pin-point it to a certain application or activity that I may have been using before the shutdown. Anyways, I decided to take a 4GB stick out and reinstall a 2GB OEM stick in there to reduce the RAM to 14GB and I am glad to say that its been over a month now with no shutdown. So it does seem that these iMacs do not like to be maxed out on the RAM. Anyways, just thought I would put in my 2cents.

P.S. I did a reinstall of Lion and that did not help. Then I also reinstalled Snow Leopard and it was still shutting down. At that point is when I decided to try the RAM fix and it worked.

I say I have had the problem since 2009 on my 2008 iMac. It was always random and it would completely shutdown. Many discussion thread suggested it's memory issue because I added non-OEM memory. But the behavior didn't feel like memory problem to me so I continue to do research on and off. Recently, I found a thread suggesting that it could be a heat managment issue. The iMac runs its fan mostly on a low rpm. When more programs are running or you are using some CPU intensive app, it causes more heat to build up in the chasis because the CPU is working harder. I don't know if you experience the same but many times after my iMac shutdown and I power it back on, the fan went into turbo speed immediately. So, it thinks it needs to use ultra high speed fan to cool itself down. That means the shutdown was due to overheating. When the iMac thinks it reaches that temperature thrashhold, it shuts down to protect itself.

So, the thread recommended using a fan control app to increase the fan speed to help cool the board better. The free app is called smcFanControl. it allows me to adjust the default fan speed to higher rpm and I can add custom speed profiles (say medium and high fan speed). it has a temperature guage telling you how hot your machine is. If I see the temperature is going up because I'm running some CPU intensive program, I can change the fan profile and have it run at higher rpm. It's a little sad that I have to monitor the temperature on my Mac but ever since I installed the app and actively manage the fan speed, I have not had one power crash.

The app is free and I'm out of Applecare coverage so I gave it a shot. Hope this helps someone out there.

iMac turn off right in the middle of working plz solve my problum...