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Fans going crazy, CPU 100% idle


26 replies to this topic

#16 OP .Neo

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Posted 30 September 2012 - 12:23

Here's an interesting blog post about the issue. You probably have already read it since it was in the first 10 results of a google search but i still post it just in case.

http://gigaom.com/ap...lion-heres-why/

Spotlight reindexing doesn't take days or weeks.


#17 Pedro3

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Posted 14 October 2012 - 12:24

Did you try to install Lion or Snow Leopard? Just to have sure that the problem is in ML

#18 Hum

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Posted 14 October 2012 - 12:40

Maybe this helps:

http://www.hddfancontrol.com/

OR:

Symptoms

After plugging in the iMac and turning it on, the fans (blowers) may be noisy and appear to run at full speed. In this event, shutting the iMac off and turning it on again wouldn't fix the issue.

Resolution

If you press the iMac power button while you are inserting the power cord, the iMac will enter a mode in which the fans (blowers) run at full speed. In order to correct the issue, reset the SMC and then start the computer by pressing the power button after the power cord has been fully inserted.

The iMac should now start up and operate as expected.

http://support.apple.com/kb/TS1433

AND:

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

http://hints.macworl...110606033134359

#19 Shadrack

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Posted 14 October 2012 - 16:23

UPDATE:

Okay this is incredibly interesting. I'm now 100% sure this is indeed a software issue, rather than a hardware related one. For whatever reason OS X Mountain Lion is telling my iMac to increase CPU fan speed in order to cool off. But apparently this is a one-way street. As time progresses the fan speed just continues to go up until it hits a maximum of about 4150 rpm. Like jamesyfx noticed they it will continue running at its maximum until I do a full shutdown. So for whatever reason OS X Mountain Lion won't tell my iMac to reduce fan speeds once it cooled off.

After a lot of Googling I noticed other people having the same issue with OS X Mountain Lion. Not just iMacs but MacBook Pros too. One person came with the suggestion to temporarily download and install iStat Menus 2, set Fan speed control to "Medium" (it's on of the default "rules") and then return to "Default". In literally an instant my iMac's CPU fan would drop from its maximum of ±4150 to a quiet 1940 and then continued to drop.

Check out the below screen shot and note the uptime: Over 6 hours and a regular CPU fan speed of 1885 (it's still dropping as I type).

So what's going on here people?


I'm confused. Did that software package end up solving the problem for you or is it still an issue?

#20 OP .Neo

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Posted 15 October 2012 - 07:42

I'm confused. Did that software package end up solving the problem for you or is it still an issue?

It solved the problem until the next restart.

#21 FightAndLive

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Posted 15 October 2012 - 07:48

Off hand I would say the temp gauges are wrong, without touching the cpu or the motherboard touch the bottom of the heat sink(while the computer is on) and see if its hot. That feels like the CPU is over heating(which would cause the 100% cpu usage).

#22 OP .Neo

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Posted 15 October 2012 - 09:54

Off hand I would say the temp gauges are wrong, without touching the cpu or the motherboard touch the bottom of the heat sink(while the computer is on) and see if its hot. That feels like the CPU is over heating(which would cause the 100% cpu usage).

I have no idea what you're talking about or why you think there is 100% CPU usage. :/

#23 iUserX

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Posted 24 October 2012 - 20:52

Buy a new iMac :p

#24 GABLAD

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Posted 15 January 2015 - 05:18

Hi there, old thread, but hopefully someone is still around.

I have an iMac 27 late-2009, 3.06 Ghz, 8gb RAM, running OS 10.8.5, and all the hardware is original (no HD swap...). So, it has a similar problem: it takes about an hour for the CPU fan to gradually speed up from the initial approx 1200 RPM to around 4000 RPM. Then, all I have to do is to put it to sleep for enough time to let the fans stop spinning (that's not even 5 seconds) and then wake it up to see the CPU fan at normal speeds. And here it goes for another hour of gradual increase... See the screenshot of the iStats Menu, the graph shows the increase in the last hour, and the three previous increase/sleep patterns... The other two fans are just fine. All of that time, the iMac is at idle, nothing running at all. My iMac isn't my main computer, so i kinda left the problem as it was, spending an hour or so every couple of months trying to solve the issue, but after these 5 years of fruitless efforts, I can't believe I haven't solve it yet! Even though I get answers a lot from forums, here's my first post in one of them (ever!), in hope it will help.

 

Here are the solutions I tried already: smcFanControl, HDD Fan Control, iStats Fan Rules... Nothing seems to be able to override the fan speeds, nothing at all! I vacuumed the air input and output... And of course, I did the SMC reset. I try to remember all the other things I tried to do, but it gets confusing after those years of diverse problem solving. I did many upgrades (and even downgrades) too but I doubt it has anything to do.

 

Even though I never opened the iMac's case (I DID open the bottom latch to replace RAM memory at some point, comes to my mind... but that's not the back case) I wonder if it has anything to do with some hardware that would just be misplaced at the factory of because of a shock while moving the computer around... 

 

Anyone has any idea? Anything I could try?

 

Screenshot:

https://www.dropbox.....57 PM.png?dl=0



#25 +warwagon

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Posted 15 January 2015 - 05:22

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#26 Decebalvs Rex

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Posted 15 January 2015 - 05:23

Might be a broken sensor on the mobo.



#27 Skiver

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Posted 16 January 2015 - 09:54

Thread Locked - Old thread, I would suggest opening your own thread