IMac : Fans run at full speed after computer turns on and male terrible noise

The noise is unbearable.
I have tried plugging it off/on, w the power cord, resetting SMC and NVRAM-nothing. Also, when I put it
to sleep mode, it goes quiet, but then goes back to sleep mode every 5 sec until i RESTART IT.
Current values show, left fan: 998 RPM
RIght fan: 1256 RPM
Please, help, I'm not a pro so use basic language, please.
<Edited by Host>

*MAKE, sorry

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Fans run at full speed after computer turns on, and a lot of times while i'm working they suddenly start blowing and won't stop. Tried the reset SMC, nothing happens. Also the unplug powercord-method does nothing.
Anyone?

Exactly what method did you use to reset the SMC, every Mac has different methods and I want to ensure you used the method for an Intel based Imac. The correct instructions are in the iMac SMC and PRAM reset link. Do the SMC reset at least 2X!

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I have a 2009 21 iMac, recently the computer became very noisy with the fans running at full speed all the time even when checking the email or just using Safari. I don't do anything crazy like 3d renderings so I don't know why the fans wont stop. I recently cleaned it but this didn't seem to solve the problem.
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Hello irisfailsafe
Welcome to Apple Discussions
Reset the SMC > http://support.apple.com/kb/HT3964
+1. Shut down the computer.+
+2. Unplug the computer's power cord.+
+3. Press and hold the power button for 5 seconds.+
+4. Release the power button.+
+5. Attach the computers power cable.+
+6. Press the power button to turn on the computer.+
Dennis

Fan running at full speed after shut down.

My brand new, three day old 8 core Mac Pro has already frozen three times. I have been reading about the screen garbage and then the freeze. That is happening with me, too. But what is going on right now as I type on my old G4 is that the fan on the new Mac Pro is running full speed and the computer has been shut down! The fan has been blowing like this for at least 30 minutes. I am hesitant to unplug. But I can't just leave the office with it blowing like that. What is going on?

Have a lot of USB stuff attached...
Apple keyboard/mouse, Kensington track ball, (then through hub) Logitech web-cam, External HD (USB) for time-machine, epson scanner, iPod USB cable, shuffle, dock, and...ah ha..may be a culprit...a Microsoft joystick for playing x-plane (when I was thinking about what I do when this happens, I said I'd switched resolutions to use xplane..but, of course, I would have had the joystick plugged in as well..this could be the one difference (I only connect the joystick when I'm going to use x-plane)).
I will experiment some tonight...shutting down with and without the joystick to see if that makes any difference.
Now that I think of it, that seems to be the one 'difference factor'...and it would be Karma to have the Microsoft hardware messing up my Mac.
I don't have any extra PCI...nothing in firewire.
Thanks for giving me a possible lead...I'll report back.
Message was edited by: midiotlv
Message was edited by: midiotlv

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Bought a new Macbook around February 2011. Yesterday all of a sudden while watching Netflix, the exhaust fan started running at full speed (Approximately 6200 RPM). I thought the machine was overheating. So I immediately shut it down and let it cool. But I noticed the machine was barely warm.
When I started it up again, it started making the same noise with the exhaust fan running at full speed. I installed SMCFanControl and I see that the CPU is barely warm - 35-37C and yet the fan is running at full speed. I looked at the CPU/HDD usage and there is barely ANY usage (~90% idle). Nothing out of the ordinary. So it definitely doesn't seem to be a heating issue.
In order to troubleshoot this I have done the following:
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Can someone please tell me what this means?

I don't know what that code means for sure, but it sounds like one of the temperature sensors may have died, so the fans just run at full to cool.
I would take it to the apple store.

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When using just normal everyday applications such as using about 30 min of Safari to surf the web or maybe something else, my fans run at full speed. I have just got a new logic board replacing my old faulty one. How can I fix the fan problem?
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Hi again Miriam,
With more news for you and iMacG5 on the fans go crazy. I just got back my computer from the repair center. After more than a week under observation, the technician told me that they just couldn't replicate the problem. They had the computer running non-stop during all this time, not even allowingit to go to sleeo mode and nothing.
The CPU fan never went beyond 2300 rpm (or so) and never went to sleep mode on and off by itself. Furthermore, they ran all possible tests and everything comes back as OK.
Right now I have a movie running on the background, together with a photo processing software open and other smaller processes and the CPU fan is running at 4361 rpm !!! the temp of the CPU is 66.3 Celsius.
Any thoughts??? It's really making me crazy because the computer was neverlike this and now it sounds like a hair dryer. I emphasized with them the fact that this just started after they changed the logic board and as coincidence after Ioaded the security update 2006_04. The technician told me it may be software related. If the computer doesn't go to sleep by itself, then he recommended to reload the operating system.
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The fan on my brand new iMac 17" runs at full speed all the time, creating an unbearable amount of noise. The activity monitor shows 99% spare time, i.e. nothing much is running.
I updated all software, checked the firmware version (it was the latest already) and performed an SMC reset. I also unplugged it for several hours, as some people have suggested.
I downloaded smcFanControl and it says that the ODD fan is running at 5200 rpm all the time. The CPU and HDD fans seem to run at normal speeds. smcFanControl also reports a cool 39 deg.
Does anyone have any idea of what to try to fix this problem?

I don't have a solution but thought I'd add a computer that showed the same behaivor.
A 20" iMac I was configuring for my company did the same thing, but just once so far. I used it briefly just out of the box and didn't have any problems. It's a stock install of OS X 10.4.8, no other software installed. Turned it on several days later and the fans ran during the 2 hours I used it to run Safari via Airport. I turned if off after it started to smell like hot electrical components. Activity monitor looks completely normal. After shutting it off for two hours, unplugging and re-plugging AC and keyboard, it came back on with no fans. I did not do the SMC reset or any updates between the power cycle.
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http://daringfireball.net/2006/04/repairpermissionsvoodoo

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Hi,
I was wondering what could be the reason for my fan running on full speed at all times?
It is pretty annoying especially when I am in a quiet room. This just started happening this morning and I thought it was just going to stop but it didn't so I restarted my MacBook and shut it down also and still no luck.
Oh...
My battery meter only says 1:45 after I just took it off the charger when it said it was fully charged and I had the green light on my charger.
What could be the reasons for these two things?
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I reset the PMU and the fan is still going at full blast right when the MacBook starts up.
Will I know that the PMU is reset or will it just fix the problem if it is?
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Fans run at full speed

As in subject, my brand new iMac Aluminium 20" 2GHz has a problem: fans run at full speed...
After reset of PRAM or SMC, fans start slowly (1200rpm) but rise ti 3500rpm after few minutes and they don't change until a new restore of SMC.
cpu 3-4%,
no apllication opened,
nothing in dashboard.
What's happen?? I've never had a problem with my mac!
PS: sorry for my bad english, I'm italian!
cerion
Message was edited by: cerion86

Hi, just an update -
I ran the Apple Hardware Test on startup, and it returned this hardware error: 4SNS/1/40000000:TpoP
I brought my machine to the Apple Store where I bought it and they ran their diagnostics and said there was nothing wrong. So when I picked it up we booted it up in the store and the fan was about 1200rpm, no problem. We ran the Apple Hardware Test in the store and it didn't give the same hardware error that I'd had before.
So, I didn't really have any ammunition to press them any further on it and for the last week it's been fine. I had the fan race on me again last night but I hope it was an isolated incident.
As for downgrading to OSX 10.4, I'd consider it but I don't feel that I should have to do that to make my hardware perform correctly.
Re. smcFanControl, I thought the purpose of that is to make the fans run faster/more often, but if anyone's used it to stop them from running too fast/too often I'd be glad to hear from you.
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(Long Version) It is hot around here these days and my computer fans seemed underpowered. I put a splitter on the case fan outlet on the motherboard and added a second fan in addition to the original fan. It all worked fine except the new fan seemed to run pretty slow. I wanted to get a voltage reading from the fan plug but I accidently touched the two sensors on my volt meter and the computer immediately shut down. It started up and worked fine except the throttle was no longer working and the fans were running at full speed. This also explained why the second fan was running slowly before when they were both being throttled.
I guess in the end I got my wish to have my fans running at full power, I just wanted to see if there will be any future problems leaving it this way.
This question was solved.
View Solution.

Hello design_guy,
You should not have any problems with the fans running at full speed other than the fact you may decrease the life cycle of the fan.
You may want to install some software on the computer that will allow you to adjust the fan speed from the computer which may help you prolong the life of the fans and give you a little control over them.
Something like SpeedFan should do the trick.
If I have helped you in any way click the Kudos button to say Thanks.
The community works together, click Accept as Solution on the post that solves your issue for other members of the community to benefit from the solution.
- Friendship is magical.

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One of my MACs (G5 2.0DP) can't slow down - the fans runs at full speed all the time (OSX 10.3.9) - hardware test - PMU - disconnect powersupply - exit single user mode - I think I did all that's in the "book" - but the fans are still running at full speed - all the time.
any ideas?

Hello,
I am not sure if you have the same issue, but I might be worth it for you to read the archive:
http://discussions.apple.com/thread.jspa?threadID=561296&start=0&tstart=0
And here is the end of my story:
Regarding my issue with the fan fan full force, yes it was resolved... but not without fighting for it!
Fortunately the machine was still under warranty, and I left it with Apple care during an oversea trip in August. End of August I picked it up suppositely fixed and after a few hours of work I noticed the same symptoms were still there! You can be sure I made it clear to Apple service I was not happy. I left the machine again for a week and 1/2 and picked it up again. They told me they replace the logic board. Again a few hours of work of testing and this time I could repeatidly hang up the machine. Back to Apple, I told them I didn't want to pick it up until they REALLY tested it! This time they replace the logic borad again, the power supply and something else?...
Anyway since then the machine works just like it did before : great, no hardware system related issues.
Unfortunately I cannot tell you for sure what was the problem: logic board? CPUs? power supply?... and I could not get the information from Apple care, especially I would have been interested in the specific procedure they follow to fix my problem... but for some reasons they don't want to share this information...
I hope your machine is still under warranty... other wise you'll have to weigh the pros and cons to have it fixed, especially if they replace the logic board ($900 I believe) or any other main components...
I hope this help,
Good luck,
David
Dual 2 GHz PowerPC G5 Mac OS X (10.4.8)

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My Western Digital 500GB hard drive crashed. The date on it is Aug. 2010. I swapped it out for a Western Digital Caviar Black 1TB. All plugs were identical including the temp sensor cable. My fans now run at full speed. What gives? BTW. This is th 3rd WD hard drive to fail at my office in multiple iMacs. I have a 21.5 iMac i3 3.06ghz. I have tried the SMC reset,.. no luck. Reset the PRAM,.. no luck. Hard drive and computer function perfectly, it just sounds like a loud annoying PC.

After a little more research the only thing I found for 21.5" mid 2010 imac were three part numbers for three sensor cables which are a function of vendor:
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Since this night my iMac's fan (summer 2012 model) runs at full speed from the beginning of powering it on. It even runs at full speed when I put the iMac to sleep!
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I have an iMac 20inch with 8GB RAM and its an i3 intel processor. I purchased it from a friend of mine who had replaced the original hard drive with another that amounts to a terabyte. Now the fans are running at full speed all the time making it way too noisy to work with. It however works smoothly with no problems except the fans are irritating, it does not heat up though. Anyone with a solution? I tried resseting the SMC it didnt work.
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See the suggestions by mende1 here > Mac fan runs all the time

IMac : Fans run at full speed after computer turns on and male terrible noise

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