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One way to fix an overheating graphics chip in an iMac Desktop Macs
My late 2006 iMac started to freeze and have graphics issues after about 18 months of use. It turned out that this was an overheating problem experienced by a lot of users. smcFanControl made the computer noisy, but didn't stop the problem, especially in the summer. I'd had the iMac sitting (unused) on a desk for a while, and was going to throw it out...but instead, I tried making a few ventilation holes, as seen in this picture.

If you want to do this yourself, you'll have to locate a service manual for the iMac (20-inch Late 2006); try a PDF search on Google. Follow the instructions in the manual, and take almost everything out of the computer. Next, drill some holes in the back with a hole saw -- the important holes are marked in the above-linked picture. Finally, install smcFanControl, and crank up the fans.

This modification makes the computer loud, but the processors consistently run at 35 Celsius, and the computer doesn't crash. I haven't tried turning down the fans yet, but it's been running for weeks without a problem.

[robg adds: I would not advocate this solution myself -- I'd either take it in for service, or donate it to someone else who could have it serviced. However, to each his/her own, and the above solution is basically free.]
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One way to fix an overheating graphics chip in an iMac
Authored by: Superboy on Jan 20, '10 08:06:31AM

Im thinking it'd be a better idea to clean out the fans, as if it cooled properly when it was new, it's most likely dust clogging it up... Seems a better idea than mutilating it :P

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One way to fix an overheating graphics chip in an iMac
Authored by: asmeurer on Jan 20, '10 08:06:55AM

OH! That picture makes me want to cry!

By the way, did you make sure that the whole ventilation system was clean of dust?

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One way to fix an overheating graphics chip in an iMac
Authored by: smitty97 on Jan 20, '10 08:29:57AM

"hint" fail!

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One way to fix an overheating graphics chip in an iMac
Authored by: Swany on Jan 20, '10 08:50:32AM

Brain surgery. I had this problem with my 2007 iMac, the same issues, smcFanControl helped a bit but the problem kept getting worse. Apple was kind enough to replace the logic board even though it was out of warranty. I think they decide on a case-by-case basis whether or not to fix the problem, they have not recognized it as a general flaw. Maybe anyone with this problem can take the picture into the genius bar and ask if they will perform some trepanation.

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One way to fix an overheating graphics chip in an iMac
Authored by: joeyblades on Jan 20, '10 09:20:07AM


My iMac failed for this problem about 2 months past the warranty period. I took it into my local Apple store. They told me my only repair option was to replace the logic board. The cost of the repair was only about $100 less than a brand new iMac... I chose the later.

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One way to fix an overheating graphics chip in an iMac
Authored by: pauldy on Jan 20, '10 09:33:42AM

Ouch, I was thining like a drill to put small ventalation hole sin the rear of the computer not the shot gun approach of holes the size of door nobs in the rear of the machine. I cringed when I saw that image, to each his own I guess.

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One way to fix an overheating graphics chip in an iMac
Authored by: bedouin on Jan 20, '10 10:16:14AM

You couldn't put a larger or more powerful fan inside? Thermal paste wizardry? The problem now is that it will suck a lot of other stuff inside it.

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One way to fix an overheating graphics chip in an iMac
Authored by: sfgecko on Jan 20, '10 10:29:22AM

a lot of people are having this problem with the 2006 imacs:

of course, apple refuses to acknowledge it as a widespread problem.

unfortunately, if you have the ATI X1600, the GPU is soldered onto the logic board, so the entire logic board has to be replaced ($600-$800). on the 24", the nvidia 7300/7600 graphics card can be replaced separately ($200-$300). but since they don't make those cards any more, the best you'll get is a "remanufactured" one, which will most likely conk out within a year.

the imac is poorly designed and makes for a better toaster. the power supply unit sits right above the 3.5" hard drive. the hard drive fan sits below the hard drive and blows hot air right over the power supply unit. this could also be why the imac experiences random shutdowns and freezes when it gets too hot.

here is a link to a fan control app specifically for the 2006 imacs:

2006 iMac Service manuals:
20" -
24" -

personally, i would not recommend an imac to any of my peers and friends. they may look nice on the outside, but inside they're a disaster waiting to happen. couple that with apple's poor QC of late, and you're spending a lot of money for sub-par products.

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One way to fix an overheating graphics chip in an iMac
Authored by: Typhoon14 on Jan 20, '10 11:20:20AM

This just doesn't make sense. If a computer just starts overheating out of the blue after working fine for over a year, it is not likely to be a design defect requiring such a drastic solution. This sounds strongly like a case of dust in the system, a broken fan somewhere, or an unrelated hardware problem that will either reoccur in the future, or that you somehow fixed by reseating everything when you dismantled the system. In any case, this seems like a really ill-advised hint and I thoroughly question whether those gunshot holes in the back of the case actually make any difference, other than to weaken the chassis and guarantee that you will suck in a ton of airborne junk.

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One way to fix an overheating graphics chip in an iMac
Authored by: cdfmrl on Jan 20, '10 11:50:16AM

Wow, that's a really bad idea!

I guess the thought is that more holes means better ventilation, which is wrong. The air flow inside the iMac (and other computers) is very carefully designed to move air over the heat sinks and other components and out the top of the case. By drilling holes in the case, you are preventing the fans from doing their job. That's like turning on the air conditioner and opening some windows!

Rob, you should remove this "hint".

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One way to fix an overheating graphics chip in an iMac
Authored by: concrete on Jan 20, '10 12:50:11PM

the funniest thing I have seen this year... clicked on the picture link not expecting to see holes like that... the arrows highlighting the in and out are hilarious. I would love to see a water cooled version if you are up for it.

I honestly do expect this to end up in the odd spot of the newspapers.

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One way to fix an overheating graphics chip in an iMac
Authored by: ObbieZ on Jan 20, '10 02:49:20PM

I cringed when I read that you were thinking of throwing the machine out.

I work for a school for special needs kids, and we have a lot of old CRT iMacs still in service. So before you throw out a 3-year-old machine, consider that there are many schools with 10-year-old machines (or not enough machines, or NO machines) who would LOVE to upgrade.

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One way to fix an overheating graphics chip in an iMac
Authored by: aalegado on Jan 20, '10 03:26:42PM

I would definitely exhaust (no pun intended) all cleaning options to return air-flow to stock condition before resorting to opening up new ventilation holes. This would involve more than just cleaning the fans and the various shaped-bits that route airsome attention would have to be paid to dirt/dust build-up on all the components in the path of the air flow. Even a small, barely visible build-up of dust on a component can drastically affect air-speed around that component. Multiply that by several components on the Mobo and you get a congested but apparently obstruction free computer. You can get away with dusty components on a computer with more free air space (the typical PC or even the inside of a MacPro) but with literally no free air space, an iMac's interior can become an aerodynamic obstacle course is short order.

After a good internal cleaning there are some other options to consider that do not require permanent modification of the iMac:

1. Put a small, low-speed fan behind the iMac to blow air onto the back of the case. If you can point the fan so it blows air "up" this will be more effective than if the fan is level with the iMac and just blowing onto its back. This additional air-flow will "wick" heat off of the back of the Mac faster than still air is capable of doing. Also, the air-flow past the iMac's ventilation slot will help to pull air through the slot.

2. Come up with a forced-air solution:This would take some fab skills but if you could fit a plenum on the outside of the iMac that covers the air intake holes and connect that plenum to a 8" PC fan you would effectively increase the airflow through the iMac in excess of what the built-in fans will be capable of. This also forces more dirt/dust into the iMac but if you can fab a plenum you can figure out how to stretch cheese-cloth or some fabric over it to filter the incoming air.

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One way to fix an overheating graphics chip in an iMac
Authored by: Neil Anderson on Jan 20, '10 05:16:56PM

Great pic! I gotta send this to my PC buddies who say Macs can't be modded! Har har.

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One way to fix an overheating graphics chip in an iMac
Authored by: joeyblades on Jan 20, '10 07:08:15PM


You don't understand. When these iMacs go bad - they are virtually dead. I can start mine up and maybe get about 15 minutes of work done and then it dies. The cost to repair is nearly what you would pay for a brand new machine - maybe better with your school discount.

I canibalized mine. Memory went to a new machine, hard disk to an external enclosure. Optical drive on the shelf waiting for new home. I'm still looking for a way to reuse the display as an external monitor - seems like it should be doable...

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One way to fix an overheating graphics chip in an iMac
Authored by: audiophil on Jan 20, '10 10:44:35PM

Well then.
I've had similar issues with an imac that was abandoned by a customer and left to the junk heap. (Not the model pictured in this comment, the older generation G5 models with the CIP design, were everything attaches to the back of the display) The proc or bridge controller was overheating. My solution was to remove the grill on the inside of the back panel;(that sits flush with the air channel for the CPU heatsink) to increase the airflow through the existing air channel integrated in the back case. after removing the small gril (with no other exterior cosmetic changes) the temp stayed lower, and the overheating -> instability/slowness issues went away.

I've done this to 3 other machines to remedy similar problems with CPU temp where new fans/cleaning weren't solving the problem.

Just a FYI for you folks out there, before you go cutting your case apart.

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thumbs up!
Authored by: astack on Jan 22, '10 09:52:12AM

I just have to say, I liked your hint. Who looks at the back of their computer anyway? Cooling is a persistent problem with these compact designs. Others suggested some things like cleaning the fans, checking to make sure they work and checking the cooling paste on the video and cpu chips. These are all good ideas, but hey, if it's the difference between having to drop $1k+ on a new machine and having one with holes in it, I think you did the right thing.

Just tell people that they're speed holes and make the computer go faster. :)

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One way to fix an overheating graphics chip in an iMac
Authored by: Scooper on Jan 22, '10 07:35:36PM

I probably should have mentioned that I was quoted around $1000 to replace the logic board by my local Apple shop. Apple refused to fix it because it was out of warranty, even though a large number of users have had similar problems. Better cooling solutions with other fans etc would be a good idea but I'm not that handy. With these holes and the fans turned up my computer works fine when it's 30 to 33 degrees C outside (86 -91 degree F). I can see it's not a solution that everyone likes, but the price suits me.

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Authored by: eugene_o on Jan 23, '10 04:29:36PM

I have a 2006 iMac with the same problem. smcfancontrol is working for me (all fans at 2000 rpm).

That said, Apple really needs to pay more attention to making sure their products do not overheat. My laptop - 1st gen MacBook Air also has problems with overheating - although it does not crash, just becomes very slow.

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Blown Motherboard and failing video card.Whats my next move?
Authored by: Imacusuck on May 04, '11 06:05:08AM

I bought an Imac 24", because it was user friendly and attractive, everything a gal could ask for. Three years later (2009)i started seeing multicolored specs on the screen, and it started shutting down more and more often. Apple store checked it out said I the motherboard overheated and i need a new video card, about $1000. He said you might as well buy a new one. I said why so it could crap out on me in 3years and another $2300 down the drain. He told me im lucky that i had the computer for four years and that thats the average life of them.Like its all a game to Apple!

So, what do i do? i have a Imac that wont stay on longer than it takes the screen to light up (that veil comes down and tells me to restart). All my information, pictures everything is trapped in this piece of crap and i'm NOT willing to buy another Imac.

Do I pay $1000 to Apple Service to get maybe 2 more years out of it?

Or, do IGet my info backed up and send this piece of Crap back to Apple Headquarters with a nice juicy letter on how much they inconvenienced me and that APPLE SUCKS (even though i was their biggest fan when i purchased it). And that making something that breaks down shortly after it's warrantee is intentional fraud and to do nothing about it is pathetic!! We are not all made of money and even if we were, it did not say on the product " disposable Imac computer". I'm soo frustrated, I could fly to their Headquarters and give them a piece of my mind!

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One way to fix an overheating graphics chip in an iMac
Authored by: bluescreen on Jun 04, '11 08:14:32AM

My iMac killed it's hard drive the first-and half year and then the entire screen/ graphics card and mobo had to be replaced at the three year mark. (luckily I had an extended warranty from Futureshop). It unfortunately began to misbehave again shortly thereafter.

I use mine to run my 54" Bravia HDTV as the extended desktop and use Eyetv and noticed numerous graphics errors lines, failure to refresh etc during overheating bouts. It occurred to me that the upper left hand corner of all iMacs has some sort of an air pocket that traps extreme heat from the graphics card there. (The rear-viewed "right" of the air slot)

To verify this, I inserted a temperature probe in the back top left hand (from the front) side of the back air exhaust slot (right side viewed from rear) around 20 cm (9") from edge. The peak-hold temperature reading there runs around 130F and often (always during malfunction or addressing error graphics lockup-freeze) exceeds 140F.

At first I mistakenly thought forcing cooler air into the bottom might reduce this but it does not. There is an air pocket there caused by the vacuum back-pressure of the internal fans, which are all trying to suck air in through limited air inlets, and blowing out the upper right side of the slot so heat just accumulates there and it just runs away

The correct and ideal simplest way to permanently fix your overheating 24" Imac (iMac6.1 iCore 2 Duo at least, and several other models) requires two fixes.

First download and install smcFanControl 2.2.2. Set it up to provide (still quiet) minimum fan speeds of 2200 rpm for HDD and 2800 rpm for CPU, leave the Optical Drive one at 600 rpm to minimize dust accumulation (or just tweak it up if/when you will be using it much)

Next obtain a 12 vdc enclosed squirrel cage fan like the San Ace B76 you need not buy a new one nor this particular (best) model, but any enclosed suction-blower fan of this type (rather than an open blade straight exhaust) is ideal. It shouldn't cost you more than $5 at a surplus shop. Get and hook it up to an old 9vdc AC adapter (around 10 vdc) to run it cooler and more quietly than full 12v speeds, since it is now sucking heat instead of blowing cold air...

TAPE (with clear boxing tape) It to the rear left corner of the back (3" from the side) so it sucks air out of the hottest point of the back slot and blows it away upwards. The fact that it is an enclosed unit makes it easy to just hold there over the slot with clear boxing tape so it sucks heat out and exhausts upwards

Your Imac will now be fixed - the air slot temps will never exceed 105F again (under heavy graphics use) and your graphics card will stop cooking.

Your iStatNano (degrees C) should read: (at 26C Ambient desktop temperature)

HDD 42
CPU 33
GPU 40
Amb 26
DVD 1 39


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One way to fix an overheating graphics chip in an iMac
Authored by: astonchan on Oct 28, '11 12:33:09PM

I wish I had read this before buying my early 2008 iMac. It failed recently. Pretty much same symptom as described here, boot up for about 5 mins and then keep rebooting. Genius quoted me $400+ replacement of LB. I'd rather throw it away! My 7 year old P4 Dell PC desktop still works fine! If I wanted to, I would be able to boot up even my 486 machine! The iMac is the worst investment I made...

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One way to fix an overheating graphics chip in an iMac
Authored by: rober648 on Oct 12, '12 07:30:24AM
Thanks so much for the great tip! Just installed an enclosed fan in hot pocket area, instantly fixes the problem. Brought my temp from 55 deg C to about 30-32 C even while gaming in windows 7 bootcamp! I've tried everything else to no avail but this works 100% . Thanks again!

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One way to fix an overheating graphics chip in an iMac
Authored by: JLG on Oct 10, '13 12:00:19PM
Outstanding, extremely helpful comment. I used one of these fans:

Slap a velcro ring around the inlet side (I put the "loop" on the fan, and the "hook" on the iMac), put a horizontal strip top & bottom on the iMac itself, and the USB power cord is just the perfect length, even on a 24" iMac.

If the overheating problem has already damaged your GPU (so you still get video artifacts and kernel panics), you can disable Quartz Extreme:

To test whether or not this will actually help you, try booting in safe mode. If it runs perfectly fine that way, then disabling QE will help.

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