2012 iMac fan sporadically running at full speed.

I purchased a 21" iMac in October. In the last two weeks, the fan has started having issues. It will intermittintely run at full speed for anywhere from 5 to 20 seconds, and then shut off, only to max out again in a minute or so. The computer itself is cool to the touch, the only programs running are Finder and Google Chrome, and it's in a well ventilated and cool area. I've already reset the SMC and the PRAM, seeing if either of those solved the issue, but it is still occuring. Anyone have any idea what might be causing this?

Could be a defective sensor. You can also try Intel-based Macs: Resetting the System Management Controller (SMC) and see if fixes it. If the computer is newly purchased, then take it to the Apple Store for repair. it's in warranty.

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Fans are running at full speed after hard drive upgrade. Used same brand drive.

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:
922-9215, Hitachi
922-9216, Seagate
922-9622, Western Digital
The strange thing here is these are vendor specific and not model within vendor specific. So you started with a WD drive and replaced it with different model, but still a WD drive. So you would think it would require the same sensor cable.
Maybe the drives are different enough for this to matter. Or maybe you should check the connections one more time. Be it model of drive or connections, whichever it is, the sensor cable is the source of your problem.

I have a dual 1.8 ghz pwer pc g5 and sometimes i put it in sleep mode and come home on my lunch break and the fan is running at full speed and the computer has frozen up...what is going on here?

and sometimes i put it in sleep mode and come home on my lunch break and the fan is running at full speed and the computer has frozen up...what is going on here? is it a virus or has my computer been hijacked? it cant be good for the computer...anyone ever had this problem..?

Your problem has been reported many times, but causes are as varied as individuals.
Can we assume that a hard shutdown allows a normal restart?
Can I assume that you have used Disk Utility from your OS X install disc to repair the hard drive directory? The freezes and hard shutdowns require that the drive be repaired (not permissions) or soon the machine won't boot at all.
If the root issue is software related, in Console (the application) under Logs, there should be loggings around the time of sleep and logs that tell you what process went wild and froze the machine.
Network activity is also a common casue.
Other info:
http://support.apple.com/kb/ht1776
If hardware related, such as an external drive, other USB device (Wacom tablet) or USB PCI card, ejecting, disconnecting, removing, or in the case of the Wacom, updating drivers, are all potential remedies.

One of my MacBook Pro's fans is running at full speed

Out of the blue today, my 2011 MacBook Pro started fans went mental when I awoke if from it's sleep. They started running at full speed, far louder than I've ever heard them before. I searched through other discussions and it suggested I try an SMC reset. I performed one of these with no success.
I then opened smcFanControl and noticed that my leftside fan was running at 7000rpm+ and the rightside fan was running at normal speed 2000rpm. It randomly spools on and off high speed and I cannot find any fixes or similar problems online. Can anyone suggest a fix for this or should I be taking it to a repairer?
FYI my logic board was only replaced in April under warranty so could it be faulty?

Hi andyBall_uk
SMC fan control measures temp also. Currently running at 47*C as you can see in the screenshot below. I tried overriding the fan speeds...works for the right fan but not the left one so it appears only the left fan has the fault.
The weird thing is, when you press your finger down anywhere on the left speaker next to the built-in keyboard, the fan slows back down to normal speed, but when you let go it speeds back up again. I might open it up in the morning to see if any of the connections are loose, because it seems weird that this happens with a small amount of pressure applied to the body. Also of you tilt the macbook it sometimes slows back down to normal speed (but sometimes stays at high speed). I will let you know how I go. Thanks for your suggestion/s

HT3964 Fans running at full speed even after SMC reset.

I have reset the SMC twice on my iMac 24" (early 2009) and my fans still run at full speed, but only after I've been away from my computer for a while. It never happens while I'm using it. Any suggestions? My Apple Care plan ran out a few weeks ago and so I can't call in without paying.

Try iStat Pro and see what temps are being seen by the system.
http://islayer.com/apps/istatpro/
I know this won't fix it but it might allow you to see which sensor might be acting up.
Have you tried a PRAM Reset? Again just fishing.
Option + Command + R + P during powerup thru 2 chime sequences

Case Fan Running at Full Speed

I accidentally shorted the case fan circuitry on my HP motherboard (explanation below) and now the fan runs at full speed all the time. Other than the fact that is was a stupid thing to do, will it be a problem long-term and should I try to reset the fan speed switch?
(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.
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Macbook May 2010 edition exhaust fan runs at full speed

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:
1. Installed latest upgrade - Snow Leopard 10.6.7
2. Reset SMC
3. Reset the PRAM
4. Tried booting from the install DVD. There as well it exhibits the same issue.
Neither of these steps have helped me with my situation. I would really hate to go to the apple store as its always crowded and would end up wasting time. Are there any other steps I could try?
Update: I tried running the Apple Hardware Test from the DVD. This is the error code that I got: 4SNS/1/40000001: TN1D- -1.000
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.

TS1433 The fan of my 2013 iMac running 10.9.5 keeps running on full speed even if there is no programs running. SMC reset is not working

The fan of my 2013 iMac running 10.9.5 keeps running on full speed even if there is no programs running.
I've tried the SMC reset, but around 5 minutes after restarting the computer the fan picked up speed again.
When trying to shut down the mac normally and turning it back on - the fan starts directly.
Thanks already for any tipps or tricks to resolve this problem!
Additional Information:
2.7GHz Intel Core i5
8GB 1600MHz DDR3

Hi @krod619 ,
Thank you for visiting the HP Support Forums and Welcome. I have about your HP Pavilion dm4 3099se Notebook and overheating error and shutting down. I would reset the BIOS with this document selecting the reloading the BIOS default settings. This will reset the fan.
Hope this helps.
Thanks.
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Click the “Kudos, Thumbs Up" on the bottom to say “Thanks” for helping!

Very noisy iMac, fans running at full speed even when performing smal tasks

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.
Anyone knows what's the problem and how can I fix it?
Thanks

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

My iMac G5 Fans run at full speed when using regular everyday applications.

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?
Thanks!

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.
Any comments appreciated.
Zwirek

Mac Fan runs at full Speed from start, even in standby mode!

Hi Folks
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!
So far I tried to reset the SMC three times, noo effect at all. I checked also the activity log, no processes or other activities are causing this. I read about defect HDD sensors, could that be the problem?
Any ideas how to fix or at least control this issue???
Thank you all for your help!
Matt
PS: That's a pretty annoying sound I'm hearing here, I feel like on the roof top of the Hancock Building at wind speed 200!

I have tried the SMC reset as instructed and the fan is running normally. It is a bit of an intermittent problem so I will monitor the performance of the computer over the coming weeks. If it persists, I will take it in to a service centre while it remains under warranty.
I guess the "cure" I had stumbled across by accident was nothing to do with turning the computer upside down, it was because I was unknowingly performing an SMC reset. The reason I turned the computer upside down was to find the serial number on the base of the stand so I could report the fault to Apple. Of course, when I plugged it back in to contact the support line, it worked fine.
Once again, thanks for your help.

Fan runs at full speed all the time

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.
ps. Repairing permissions is Voodoo
http://daringfireball.net/2006/04/repairpermissionsvoodoo

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.
Maybe the 10.5.2 version of the OS will take care of this problem, if indeed a problem exists.

HT3964 Fans running on full speed constantly

Hi.
I've had this problem for a while now and I'm not sure what else to do, short of taking it to an Apple authorised dealer to be looked at. The fan on my iMac Intel 24" has been running at full speed straight from when I turn the machine on. I have looked at numerous articles on the problem and have just tried the one on apple support for resetting the SMC but it still has had no effect.
Has anyone else had this problem and know how to solve it?
Thanks!

Contact Apple Service, iMac Service or Apple's Express Lane. Do note that if you have AppleCare's protection plan and you're within 50 miles (80 KM) of an Apple repair station, you're eligible for onsite repair since yours is a desktop machine.

TS1433 Fans run at full speed after computer turns on

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!

2012 iMac fan sporadically running at full speed.

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