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You are here: MacNN Forums > Hardware - Troubleshooting and Discussion > Mac Desktops > iMac Core i7 fan regularly coming on now - annoying

iMac Core i7 fan regularly coming on now - annoying
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Eug
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Oct 7, 2010, 09:54 PM
 
I have the first 27" Core i7 iMac, and when I first got it was almost always dead silent.

Now when it is idle it is dead silent but after some not too heavy usage, the fan comes on and is annoying loud. It's not vacuum cleaner loud, but it's like a forced air heating vent on my desk.

Anyone else encounter this issue? The fan is on right now, and iStat says this:

HD temp: 49C
CPU temp: 47C
GPU diode: 42C
Mem Controller: 37C
Optical Drive: 34C
Power Supply 2: 53C

Optical Drive: 3491 rpm
Hard Drive:1564 rpm
CPU Fan: 939 rpm

Are any of these unusually high?
     
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Oct 7, 2010, 11:12 PM
 
The optical drive fan (which also cools the GPU) is very high. Mine is around 1000 rpm when idling, IIRC, and even when doing crazy GPU benches it never got annoyingly loud.
The new Mac Pro has up to 30 MB of cache inside the processor itself. That's more than the HD in my first Mac. Somehow I'm still running out of space.
     
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Oct 8, 2010, 12:08 AM
 
Hmmm... I shut it down and rebooted. Now it's dead silent, with the optical drive fan at 999 rpm. The temp is 32C, which is the same as it was just before I rebooted a couple of minutes ago. I had left the thing relatively idle for quiet some time, but the fan just stayed on, at around 3500 rpm. There was no disc in the drive, and I was just surfing.

I wonder if this is a software issue, or a fan hardware issue.

BTW, a restart didn't fix it. The fan remained loud. Then I did a complete shut down, then turned it back on. Only then did the fan speed drop to 999.

Interestingly, my GPU diode is now 54C, which is 12C higher than before, and my GPU heatsink is 52C. So, this could be a GPU cooling issue maybe. However, I wasn't doing anything GPU intensive AFAIK.

Could dust cause anything like this?

---

EDIT:

Aside from just displaying the Dashboard and iStat, etc., it has been completely idle. The fan just came on, and I quickly glanced at the GPU Diode temp. It was 55C. The fan went back off again after a couple of minutes with a GPU Diode temp of around 51C.

I left it alone, and the temp climbed back to 55C, and the fan came on for less than a minute. This is unacceptable if it's going to be constantly cycling on and off even at idle. I'm gonna have to take it in.

BTW, what GPU temp do you have at idle, and at max?
( Last edited by Eug; Oct 8, 2010 at 12:29 AM. )
     
Eug  (op)
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Oct 8, 2010, 12:34 AM
 
AHA!

The fan just came on again, and I had a quick glance at iStat. The GPU Diode temp was at 55C, but iStat registered a split second temp of 126C for the GPU Heatsink reading, when normally it's within about 1 degree of the GPU Diode temp. After about 3 seconds with the fan on, the GPU Heatsink temp drops back to right near the GPU Diode temp.

I wonder if it is indeed a hardware issue, with the GPU Heatsink temp sensor going erratic when the temp climbs a bit.







( Last edited by Eug; Oct 8, 2010 at 12:52 AM. )
     
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Oct 8, 2010, 12:55 AM
 
The test they run at a repair shop should flag bad temp sensors. It's one of the few things the test seems to be good at.
     
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Oct 8, 2010, 01:01 AM
 
Well, time to do a complete cleanup of this machine, and secondary backups. Glad I got the Blu-ray drive last week.

BTW, I also note a very slight splotchy discoloration in two spots of the screen. It's not on the surface - looks like it's underneath the glass. I wonder if that's something they can fix too.

I'm still in the first year (barely), but I do have AppleCare.
     
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Oct 8, 2010, 09:45 AM
 
Speaking of "clean up," have you used a vacuum cleaner on it? It could be that things are just dusty inside and that's reducing cooling efficiency. I'd do that before hauling the thing back to the Apple Store-it could be a fix, and if it isn't, you can tell the Genius guys that it's been vacuumed out to make sure it wasn't just dusty...(as a former bench technician, I can tell you that this is something they'll likely appreciate.)

Glenn -----OTR/L, MOT, Tx
     
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Oct 8, 2010, 10:16 AM
 
How would I vacuum it out? Wouldn't I have to remove the back to do that?

I thought most of the innards of the Core i7 iMac are not user serviceable (unlike the beautiful G5 design).

Aside: I don't go usually to the Apple Store anymore for repairs. It's a madhouse there, and the guys at the other Apple service centres seem to know just as much, and can sometimes even offer used parts for out-of-warranty service if you want to save a few bux.
     
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Oct 8, 2010, 10:36 AM
 
Apply the vacuum hose to the vent slots/holes at top and bottom, and be patient and thorough. I'd start with the bottom so that there would be less chance of pulling stuff that was down there through the rest of the computer.

Glenn -----OTR/L, MOT, Tx
     
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Oct 8, 2010, 10:54 AM
 
If you are still running on your original install and haven't ever erased the drive, you can run the Apple Hardware Test. Just boot holding D and it should load the test for you.
I have plenty of more important things to do, if only I could bring myself to do them....
     
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Nov 12, 2010, 10:07 PM
 
The Apple Genius bar ran some sort of hardware test over the network. Everything checked out A-OK. So, they're going to run some other sort of more comprehensive hardware test. Hopefully it finds the fault, because this problem only happens once a week or so for me. They also checked Activity Monitor in my account to see if there were any suspicious processes, but found nothing.

BTW, they said the screen discolouration may be dust behind the glass. They're going to remove the glass to try to clean it.

P.S. The Apple Store Genius Bar is a complete zoo, and it's hard lugging around a 27" iMac from a downtown parking lot several blocks to the mall. Next time I might go to one of the independent shops outside downtown, at least if it's a ginormous iMac that is.
     
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Nov 13, 2010, 12:55 AM
 
Originally Posted by Eug View Post
The Apple Genius bar ran some sort of hardware test over the network.
That new network test that Apple has created is a joke. It's only going to find the MOST OBVIOUS of problems.
Everything checked out A-OK. So, they're going to run some other sort of more comprehensive hardware test.
Good. That test is actually useful.
Next time I might go to one of the independent shops outside downtown, at least if it's a ginormous iMac that is.
As an employee of an Apple Specialist shop, I would love to see you give the independents a shot. We never have new stuff nearly as fast as the Apple Stores, but we do try to compete with service.
     
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Dec 3, 2010, 11:07 PM
 
I got the computer back. Or rather, they gave me a new machine. They tried fixing the old one, but after the fix the hardware tests still failed. The new one is actually a slightly faster i7, but unfortunately they didn't configure it correctly. They gave me half the memory and half the hard drive space. Arrgggh!! I guess I'll be calling again tomorrow.

Actually, they did give me the old hard drive back. Just the bare drive, with some sort of mounting bracket. Not that it helps me for the iMac itself though.
( Last edited by Eug; Dec 3, 2010 at 11:23 PM. )
     
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Dec 4, 2010, 10:10 AM
 
They aren't that hard to swap out. You need some suction cups to get the glass off then the HDD is just behind the panel. Its keeping the dust out when you reassemble which is tricky.
I have plenty of more important things to do, if only I could bring myself to do them....
     
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Dec 4, 2010, 11:45 AM
 
Well, I'm certainly not going to do it myself, given that it's under warranty, and they made the mistake, not me.
     
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Dec 4, 2010, 04:22 PM
 
So, with the 2010 i7 iMac, is this normal? Notice the HD fan is 0 rpm. There is also a faint clicking noise that's barely noticeable.



BTW, ambient isn't 12C. It's more like 19C.
     
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Dec 4, 2010, 07:19 PM
 
Ehm, no. HD fan should not be at 0rpm. Mine's at 1100 rpm right now. The temps look fine though (my ambient is 16C right now, and that's not right either).
The new Mac Pro has up to 30 MB of cache inside the processor itself. That's more than the HD in my first Mac. Somehow I'm still running out of space.
     
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Dec 4, 2010, 07:24 PM
 
What's strange is if they forgot to plug in the temp sensor, it would be on full blast.. Or if the temp sensor fails it should go full blast..

Perhaps the fan itself isn't plugged in.
     
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Dec 5, 2010, 07:47 AM
 
That's what it looks like - that the fan is completely unplugged.
The new Mac Pro has up to 30 MB of cache inside the processor itself. That's more than the HD in my first Mac. Somehow I'm still running out of space.
     
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Dec 5, 2010, 08:04 AM
 
Work it a bit harder and see if it comes on?
     
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Dec 5, 2010, 06:17 PM
 
Pretty sure it should never show zero. Not 100% certain though.
     
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Dec 5, 2010, 06:21 PM
 
With Intel LGA775 based motherboards, some will turn off the CPU fan if the processor isn't running above 19˚C. The hardware monitor registers 0rpm but the fan twitches. Took me a while to realise the fan wasn't broken.
     
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Dec 5, 2010, 07:08 PM
 
I'll see if I can install istat on some of our demo machines tomorrow.
     
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Dec 5, 2010, 08:27 PM
 
Yeah, this is a brand new Core i7 (2010). I wonder if the quiet "click" I hear is the fan twitching. However, according to iStat pro, the fan registering zero is the hard drive fan, not the CPU fan. It is iStat pro 4.92, and running the disk tests with Xbench did not activate the HD fan. I wonder if the program needs to be updated.

However, it may all be moot. Apple won't add in new memory and swap the hard drive out. They are considering ordering an entirely new machine. I guess the one I have now is going to the refurb store. It's otherwise brand new too. I haven't unpacked anything else. The plastic protector on the screen is still even there.

BTW, their data/account transfer process isn't the greatest. A few of my apps (like iperf) don't work because the default install doesn't include Rosetta.
     
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Dec 21, 2010, 11:08 AM
 
Over two weeks later and I'm still waiting for the new replacement.

The good news though is for some reason they offered to get me a machine not with 4 x 2 GB SODIMMs. Instead, they offered me one with 2 x 4 GB, leaving 2 slots open. I hope that's true.

For the entire 2 weeks, this machine has been completely unused, except for the initial boot to check the specs, and to delete my personal data from their not-so-good data transfer. Somebody is going to get a very nice refurb iMac soon.

Hopefully I'll get another completely new iMac. The one sitting here was a new configure-to-order, not a refurb, and I think they're doing the same for the 2nd replacement.
     
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Jan 4, 2011, 10:18 PM
 
Sweet





Originally Posted by Eug View Post
So, with the 2010 i7 iMac, is this normal? Notice the HD fan is 0 rpm. There is also a faint clicking noise that's barely noticeable.



BTW, ambient isn't 12C. It's more like 19C.
The HD fan now displays fine. However, I think it's because the widget has been updated since I last used it with the other two 27" iMacs.



So, two months without my iMac, but maybe it was worth it:

1) 2.8 GHz --> 2.93 GHz
2) 4 x 2 GB --> 2 x 4 GB with 2 slots empty. I wish I had a reason to upgrade to 12 GB. Maybe I will when 2 x 2 GB drops to $40.
3) ATI Radeon HD 4850 512 MB --> ATI Radeon HD 5750 1 GB
4) Got my old 2 TB hard drive back
5) Got an extra Bluetooth wireless keyboard and Magic Mouse.
     
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Jan 4, 2011, 10:31 PM
 
Nice upgrade. Well worth the trouble I'd say.
     
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Jan 4, 2011, 10:48 PM
 
Originally Posted by Eug View Post
The HD fan now displays fine. However, I think it's because the widget has been updated since I last used it with the other two 27" iMacs.

Nope. It's the same iStat pro 4.92. Weird.

Originally Posted by Eug View Post
Yeah, this is a brand new Core i7 (2010). I wonder if the quiet "click" I hear is the fan twitching. However, according to iStat pro, the fan registering zero is the hard drive fan, not the CPU fan. It is iStat pro 4.92, and running the disk tests with Xbench did not activate the HD fan. I wonder if the program needs to be updated.
     
   
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