Why is my imac shutting down by itself?

Yeah, I agree with you, cezi.

I had took it to Apple Genius Bar, but it anything seems didn't help,

anything didn't changed, and the problems occured again and again.

Feeling hopelessly and getting frustrated.

Ceiz, I am now desperate. Yet to decide whether to take to Apple service or not since there are lot of incidents of failed repair of similar shutting down symptoms. To spent money again on a faulty machine is risky since its uncertainty of of the result. Do you know any case of failed repair with which Apple replaced with new machine?. In my opinion Apple should recall similar systems

Rajiv

rajiv, what are your options? do you want to live with a machine that shuts down at unexpected moments? maybe, but i guess not;

next option: putting your imac in a closet and forget about it, no you don't want that either;

so you want to put some/more effort to solve the problem; have you spent enough time on the internet browsing hours for threads that might give you a clue and something new to try out (like reducing the amount of ram, bringing down the heat etc.);

if you have been through all this i would bring it to an apple repair centre asking them for a quotation of the costs to fix the problem;

when you are ready to pay this money i would demand that they fix the problem for this money and if it comes back from the repair centre and it is not fixed they should give it another try, on their expenses, as long as is needed to really fix the problem

replacing imac with a new one: yes, i am sure i have read this has happened but, of course, it also depends of the age of the machine, an imac that is not even one year old is more easily switched for a new one that a machine that is already 3 years old

Hey guys, I searched some forums in Chinese and found that,

the problems might be and nearly caused by the problem of power supply.

There're many user was suffering in this matter and,

some of those are got help from Apple by asking to check power supply component.

there are many posts in different threads that point to power supply as the culprit; on the other hand it certainly is nog the only cause of the sudden shutdowns; and even in the case where the power supply was analyzed as the problem and replaced by apple the problem was not solved (in a number of cases) and shutdowns returned after a while;

shutdown causes:

1 = power supply

128 = ram

i replied to fast, this is the correct list:

in my case 128 appeared to be the ram

Why the sudden shut down were affected by the Ram???

a lot has been written about this subject in other threads; in short: shutdowns were caused by the 16 gb ram (4x4) in imacs; solutions:

a. lower the amount of ram (i replaced 2 4gb modules by 2 2gb modules)

b. use original ram/samsung modules instead of other brands like crucial and hynix

i replaced my 2 4gb hynix with 2 2gb samsung modules and the problem never came back (almost a month now where i had multiple shutdowns everyday)

What if I had 16gb ram (8gb x 2)?

What the ultimate solution you can give me?

can't remember reading anything about 2x8 gb

is that what you are using? why not give it a try and replace it with another combination of modules;

take some time to read this thread:

https://discussions.apple.com/thread/2473276?answerId=28465888022#28465888022&tstart=0#28465888

Ya...It seem helpful and trying to reading all posts.

Hope my mac will not shut down before I read all the posts.

Thanks Cezi.

i have an imac 27inch late 2012 model. its been good for a few years till last year when it started shutting down randomly. it did that every few days. somehow it stopped and i thought the problem went away but it returned this year. it got much worse. it was shutting after about 15mins. i had to keep unplugging for about a minute and then plug it in. the two resets suggested for macs didnt have an effect at all. the imac didnt feel hot at all so it cant be a temperature thing. it was so frustrating not finding a solution online. and i thought no way am i wasting time taking it to genius bar. i was resolved to just selling it and getting a macbook pro.

i decided to unplug the cord from the imac body and also at the socket. i left it this way at night for about 12 hours. came back and the imac didnt shut itself off again. somehow it worked. now i continue to unplug when im not gonna be using it for several hours. the imac hasnt had a random shutdown since then. and also when it goes to sleep it wakes up again when i come back to use it. its been 2 weeks now and its been a success. im enjoying my beloved imac again.

hopefully it works for some people out here.

cheers

Thanks for this—I've been pulling my hair out trying to figure out why my Mac would try to log itself out late every night.

I run an entire creative floor of Macs and I didn't know that this option existed, let alone that it was activated on my machine.

Remaining hair = safe for now.

Well, I've found this thread and read through all the posts to try and find out why my 24" 2009 iMac is shutting down.

There are many different ideas as to why this is happening, probably some are true, but cannot apply in all circumstances.

I have tried in vain to replace the power supply, graphics card and now logic board but it still switches off by itself.

I am getting the -128 error on shutdown which apparently is the RAM, but after changing this to another manufacturer I am still getting a switch off.

I can reliably get it to fail on the iMac by firing up all the applications at once soon after logging in.

I am now thinking that this is either the mains power supply cables or the LCD itself.

Potentially it could be something like a sensor or fan, but I'm not sure.

I've even thought it could be my keyboard or mouse and have changed these out too!

Also have the imac shutting off by itself problem. imac is now at the Apple store for the third time. First two times they were not able to replicate the problem, but of course 15mins into my house and it happens again.

I've tried everything from a factory reset, to formatting the drive and clean installing the OS, to installing fan control software, etc. but I still have the problem.

This time they called and said they have found the problem: they think it's the Read Housing Enclosure. Has any body ever heard of why this could possibly cause the imac to shut off? (at this point I think Apple is just reaching for straws).

tks