Why would iMac suddenly power down
January 11, 2011 5:35 PM Subscribe
What could be causing my iMac to suddenly switch off -- not shut down, but rather switch off as if the power had been cut?
I have a newish (less than 2 mos. old) 27" iMac. It's just as it came out of the box, except that I have swapped/added 16GB of Crucial RAM into it.
It's working fine, EXCEPT that 3 times in the last week or so it has SUDDENLY switched off in the process of using it.
I don't mean a slow 'shut down' in a software way, but rather that it suddenly switches off just as if I had yanked the power cord from the wall.
[Adding to the weirdness, the last two times it has happened, it has been right after I clicked a Firefox tab in the upper left hand corner of the screen. I know this sounds a bit 'tinfoil hat' because I don't know how that could suddenly cause a power loss in the iMac, but thought I'd mention it.]
Other data:
(1) no other lights / electrical appliances in the house fail when it happens.
(2) I've considered that it might be the (cheap, off-brand) power strip that I have intermediated between the iMac and the outlet. I could try replacing this, but want to know if anyone has any other ideas first?
I have a newish (less than 2 mos. old) 27" iMac. It's just as it came out of the box, except that I have swapped/added 16GB of Crucial RAM into it.
It's working fine, EXCEPT that 3 times in the last week or so it has SUDDENLY switched off in the process of using it.
I don't mean a slow 'shut down' in a software way, but rather that it suddenly switches off just as if I had yanked the power cord from the wall.
[Adding to the weirdness, the last two times it has happened, it has been right after I clicked a Firefox tab in the upper left hand corner of the screen. I know this sounds a bit 'tinfoil hat' because I don't know how that could suddenly cause a power loss in the iMac, but thought I'd mention it.]
Other data:
(1) no other lights / electrical appliances in the house fail when it happens.
(2) I've considered that it might be the (cheap, off-brand) power strip that I have intermediated between the iMac and the outlet. I could try replacing this, but want to know if anyone has any other ideas first?
Can you live without the extra RAM for a week to see if the shutdowns reproduce?
posted by germdisco at 6:13 PM on January 11, 2011
posted by germdisco at 6:13 PM on January 11, 2011
(I have used Crucial products in several machines without any problems, but you should absolutely do this before contacting Apple.)
posted by germdisco at 6:13 PM on January 11, 2011
posted by germdisco at 6:13 PM on January 11, 2011
I suspect a bad outlet, loose power cord or bad power strip.
Before you drive yourself nuts, first, make sure the power cord is secure in the wall and the computer, then move it to a different outlet and don't use the powerstrip, see if it continues... then add the powerstrip back, see what happens.
posted by HuronBob at 6:18 PM on January 11, 2011
Before you drive yourself nuts, first, make sure the power cord is secure in the wall and the computer, then move it to a different outlet and don't use the powerstrip, see if it continues... then add the powerstrip back, see what happens.
posted by HuronBob at 6:18 PM on January 11, 2011
You might want to check the Apple support forums to see if others have encountered a similar problem. Apple hardware test in extended mode wouldn't hurt either.
posted by thatdawnperson at 6:20 PM on January 11, 2011
posted by thatdawnperson at 6:20 PM on January 11, 2011
I'd be surprised if it was the RAM. If it's not the power strip failing on you and if your chord is, indeed plugged all the way in, it could be a faulty power supply.
posted by matt_od at 6:29 PM on January 11, 2011
posted by matt_od at 6:29 PM on January 11, 2011
Had this on my netbook. Turns out there was a crimp in the power cord. Looked like it was getting mains power, was really running on the battery. Battery got too low, it turned off without shutdown.
posted by orthogonality at 6:51 PM on January 11, 2011
posted by orthogonality at 6:51 PM on January 11, 2011
Is it always when you're using it in the same general sort of way - i.e. perhaps beating the hell out of it with an iMovie export or something similar? If so, it's possible that you're tripping a thermal failsafe or a power supply that just can't meet the demand. Do you have "boot from power loss" turned on in the Power Saver preferences? And if so, does it immediately come back up (like it lost power momentarily) or does it wait for you hit the power button?
posted by Kyol at 7:03 PM on January 11, 2011
posted by Kyol at 7:03 PM on January 11, 2011
I recently corrected a problem with the exact same symptoms on my [completey different manufacturer] brand laptop.
As Kyol mentions it was from thermal overload, because my CPU fan was blocked by dust. Disassembly cleaning, reassembly corrected it.
posted by oblio_one at 7:54 PM on January 11, 2011
As Kyol mentions it was from thermal overload, because my CPU fan was blocked by dust. Disassembly cleaning, reassembly corrected it.
posted by oblio_one at 7:54 PM on January 11, 2011
I have had bad RAM cause a mac to crash unpredictably - just tonight, most lately, in fact; it was a bad stick of new RAM.
Have you tried Applications > Utilities > Console.app to look into console.log and system.log? If there is mention of bad writes or accesses, or a kernel panic in there at the dates/times in question, it makes the bad RAM theory much more likely.
You can check your RAM by following the instructions here. It takes quite some time to run that test.
posted by Protocols of the Elders of Sockpuppetry at 9:11 PM on January 11, 2011
Have you tried Applications > Utilities > Console.app to look into console.log and system.log? If there is mention of bad writes or accesses, or a kernel panic in there at the dates/times in question, it makes the bad RAM theory much more likely.
You can check your RAM by following the instructions here. It takes quite some time to run that test.
posted by Protocols of the Elders of Sockpuppetry at 9:11 PM on January 11, 2011
I'm betting on a bad power supply. Firefox briefly uses insane amounts of CPU as it starts, and also as it flips tabs if the tabs have lots of content. If your PSU is marginal, the increased draw due to this could be making it lose regulation and crowbar itself off.
In any case, it doesn't really matter what the problem is; you're still under warranty. Whip out the extra RAM, make sure the problem still happens with only Apple stock RAM fitted, then back you go for a warranty replacement. In theory, fitting third party RAM shouldn't cause you warranty hassles; in theory, there's no difference between theory and practice.
posted by flabdablet at 11:04 PM on January 11, 2011
In any case, it doesn't really matter what the problem is; you're still under warranty. Whip out the extra RAM, make sure the problem still happens with only Apple stock RAM fitted, then back you go for a warranty replacement. In theory, fitting third party RAM shouldn't cause you warranty hassles; in theory, there's no difference between theory and practice.
posted by flabdablet at 11:04 PM on January 11, 2011
Response by poster: Thanks everyone for your suggestions so far. The problem hasn't happened again yet, but I'll try all simple remedies first (refit power cord, new power strip, try with Apple RAM back in) and if it keeps happening then yeah, I think flabdablet's idea of a bad power supply must hold. I hope not, 'cause that would suck to have to reset up a new computer! I will let you all know.
posted by meadowlark lime at 6:14 AM on January 12, 2011
posted by meadowlark lime at 6:14 AM on January 12, 2011
Sounds like thermal overload to me.
Try stressing your system with some intensive processing task and see if it shuts down. It might also depend on the surface your laptop is on while you are doing this. Sometimes things like using a laptop in bed, on your couch or lap can smother all the vents and make heat build up.
posted by srboisvert at 7:26 AM on January 12, 2011
Try stressing your system with some intensive processing task and see if it shuts down. It might also depend on the surface your laptop is on while you are doing this. Sometimes things like using a laptop in bed, on your couch or lap can smother all the vents and make heat build up.
posted by srboisvert at 7:26 AM on January 12, 2011
Response by poster: srboisvert: "Sounds like thermal overload to me.
Try stressing your system with some intensive processing task and see if it shuts down. It might also depend on the surface your laptop is on while you are doing this. Sometimes things like using a laptop in bed, on your couch or lap can smother all the vents and make heat build up."
I think this might be the real solution. The shutdown just happened again for the first time since I posted this. It happened when I was running Firefox with about 10 open tabs and watching an .avi with VLC.
How else can I test it? Should I try running 20 .avi's simultaneously?
Just to be clear, this is an iMac, not a Macbook, so there's no issue of blocking the fans.
posted by meadowlark lime at 7:26 PM on January 16, 2011
Try stressing your system with some intensive processing task and see if it shuts down. It might also depend on the surface your laptop is on while you are doing this. Sometimes things like using a laptop in bed, on your couch or lap can smother all the vents and make heat build up."
I think this might be the real solution. The shutdown just happened again for the first time since I posted this. It happened when I was running Firefox with about 10 open tabs and watching an .avi with VLC.
How else can I test it? Should I try running 20 .avi's simultaneously?
Just to be clear, this is an iMac, not a Macbook, so there's no issue of blocking the fans.
posted by meadowlark lime at 7:26 PM on January 16, 2011
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