27" iMac Hard Drive Fan Problem

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Level 1

1 points

27" iMac Hard Drive Fan Problem

I have a 27" iMac with 3.06ghz processor 1tb hdd and 4gb of ram purchased around march and I am having a weird problem with the hard drive fan. I brought it to the genius bar and they said the problem was with a program i was running(I dont believe them). I find the problem to be strange. I keep my computer running all the time and restart from time to time but rarely shut down. I noticed that the fan was running at high rpm's and they only solution was to shut down and restart would do nothing to resolve the problem. Then I noticed up in the next week that the same problem was happening. I started noticing a trend it was happening at the same time every week on the same day. I look up if there is anything in Activity Monitor causing the problem and I find nothing. Currently the only apps I have running mostly are Google Chrome, Mail, Adium, Itunes, Echofon and Dropbox. I wouldn't think that any of these apps are causing this problem. Anyone have any idea what could be causing this problem? Any help will be appreciated.

27" iMac, Mac OS X (10.6.4)

Posted on Aug 1, 2010 5:46 PM

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Answer 1

AnybodyM

Level 1

4 points

May 24, 2017 3:25 PM in response to JMWhitt

Had the same problem on a 27" iMac with the Core 2 3.06ghz CPU ("Late 2009").

Every couple of days/weeks the fan was running at top speed without any discernible cause (this iMac is on 24/7). System had always to be restarted for the fan to return to normal. This happened in Windows, as this iMac is used exclusively as a Windows 7/8/10 PC and MacOS was only installed a few times to perform Firmware updates and set up Bootcamp.

It was really annoying. Then the harddrive started dying which set in motion plans we had previously to replace it with a SSD. The original harddisk had an extra temperature sensor cable. Those two wires were clipped together by me to set the fan to off/lowest speed possible since the SSD (1TB Crucial BX100) doesn't really get that warm anyway. Then we proceeded to install the SSD, i think we just fixed it using double sided tape (I don't remember exactly, this was about a year ago).

Since we did this, the "fan at high speed once a week" problem has NEVER reappeared. I think the hard disk is at fault and sends a faulty signal through the 2-wire-temperature sensor after some time. Replacing the HDD with an SSD was worth it anyway, and it's really nice that the fan problem was solved too.

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Answer 2

Sep 23, 2017 5:54 PM in response to JMWhitt

Found that removing the Drive controller from the old HDD (it's connected with just a couple torx screws) and wrapping the drive controller card in piece of cellophane and connecting ONLY the heat sensor to the card of the old HDD (all other connections to the new hdd) This allows the heat sensor to function and register temps (the cellophane prevents metal from contacting other components) don't make the cellophane tight, this is where airflow is helpful in getting the heat to the sensor to control the fan. It takes minimal space and seems to function without needing to make changes to the underbelly of OSX (MacOS)

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Answer 3

rkaufmann87

Level 10

144,150 points

Aug 1, 2010 6:04 PM in response to JMWhitt

Welcome to Apple Discussions.

My guess is it sounds like a software problem. I think you might be on the right track finding out what is by using Activity Monitor. When the fan speeds up open AM and check to see what is using the most CPU cycles, if you see something taking up quite a bit that is probably the offending application. Any one (with the exception of Mail & iTunes) could be causing the problem.

Regards,

Roger

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Answer 4

Aug 1, 2010 6:34 PM in response to JMWhitt

Have you tried resetting the SMC? Also, I'm going to side with the Apple people if you're using some program to try and control the fan speed. That's just not a good idea. If it's just monitoring fan speed, then I'll be on your side saying it's unlikely to be the cause of the problem.

But resetting the SMC is the first step in troubleshooting here. If that doesn't fix it, you will have to get a little more forceful. In my experience, the "Genius Bar" seems more interested in finding some excuse to get you right back out the door if you're not going to buy something or it's going to take more than 5 minutes.

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Answer 5

den.thed

Level 10

82,570 points

Aug 1, 2010 7:07 PM in response to JMWhitt

Hi JMWhitt

Welcome to Apple Discussions

In addition to Roger and Scott's great input, I've also seen a few folks come thru here with real 1TB HD temperature sensor issues. Download the iStatPro widget and periodically monitor your temperature stats, then the next time the fan(s) kick up compare those temperature stats.

http://www.islayer.com/apps/istatpro/

Dennis

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Answer 6

JMWhitt Author

Level 1

1 points

Aug 1, 2010 7:22 PM in response to den.thed

Yes I have iStat Pro installed in Dashboard and have monitored the rpm's of the fan and the temp of the hdd itself the rpms are in the high 4000's and the temperature is around 100 degrees.

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Answer 7

JMWhitt Author

Level 1

1 points

Aug 1, 2010 7:35 PM in response to Scott Billings

Going to try to reset the SMC but won't know if it works for another week because the problem is accuring weekly so hopefully that works.

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Answer 8

TysonF

Level 1

0 points

Oct 18, 2010 8:36 PM in response to JMWhitt

I have the same imac (3.06, 27 inch, etc) and I have two logic boards replaced plus one graphic card and still have issues with the load fan noise... I am tired of "sending it in" for service... It has been a problem since the first 60 days of purchase... My graphics card was replaced because I had an issue with my screen mirroring itself... what was on the bottom was also on the top of the screen. I have to take it in again on Wed ... so we will see. They said that if it happens again they will discuss about replacing the unit... I personally don't want it anymore with all the troubles... I would take a i5 or i7 though and just "deal" with the issue if it occurs.

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Answer 9

JMWhitt Author

Level 1

1 points

Oct 22, 2010 2:57 PM in response to TysonF

I reset the SMC and did not resolve the issue. So I took the action to do a reformat and reinstall the OS figuring this would clear up and third party software related issues. Waited a week and the same thing is still happening. Really dont get why or what is causing this to happen its not like the HDD is running hot or anything according to istat. I called Apple Tech Support and will be bringing it in to a Authorized Repair center because my Apple Store keeps giving me the same story.

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Answer 10

Dec 7, 2010 1:23 PM in response to JMWhitt

For me exactly the same problem. Just bought my imac last friday....
The fan is making me crazy, tried to reset the SMC, didn't solve the problem. I don't know what to do.

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Answer 11

ric2z

Level 1

0 points

Dec 7, 2010 11:18 PM in response to JMWhitt

I bought my mac in september, and I've had the same problem since I opened the box.

When the computer is turned on, it gradually accelerates the hard drive fan speed until it's just too annoying to be used; 7000rpm, more or less... Maybe more.

I called apple, and they said to take it to a mac repair shop; they didn't do anything...

I still have the problem, and resetting the SMC did not help.

Please help!

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Answer 12

paulha

Level 1

0 points

Dec 8, 2010 2:04 AM in response to JMWhitt

I have a 21.5" iMac that is doing the same thing. Every week I have to shut down the computer and restart it because it's fan goes into overdrive. I've had mine for almost a year now (purchased it in January 2010. It's driving me crazy too. I have tried resetting the SMC and that doesn't help. Every week without fail it happens. I have even left it running with NO programs running and it still does it.

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Answer 13

Ali O.

Level 1

0 points

Jan 6, 2011 1:08 AM in response to JMWhitt

I purchased my iMac in december last year and the noise of the fans drove me crazy. I finally found a solution which is kindof techno but now I at least have a nice iMac that I can enjoy in silence.
The thing is to slow down the harddisk fan rotation speed. You can do that by using a program called smcFanControl to set the maximum speed of the fan. The GUI of smcFanControl doesn't allow you to do that, you'll have to do it in a terminal window.
In a terminal window do the following:

/Applications/Utilities/smcFanControl.app/Contents/Resources/smc -k F1Mx -w 2af8

For example, this will set the maximum RPM of the HDD fan to 2750.

The -k parameter is the HDD fan for the iMac. The -w writes the value of the RPM which is the hexadecimal representation of 4 times the RPM (i.e, 4 x 2750 = 11000 which is 2af8 in hex representation). Don't ask me why, but that's how it works.

I noticed that you have to run that line above each time you log in, so you might have to automate it.

Hope this helps.

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Answer 14

dughutch

Level 1

0 points

Jan 10, 2011 12:19 AM in response to Ali O.

Confirmation - the fix as posted works on my 27 inch iMac. My problem appears to be the same as others here, the HDD fan ramps up around 4500 RPM at 0300 in the morning. It appears to happen only every couple of weeks, maybe? Rebooting the box also resets it.

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Answer 15

JMWhitt Author

Level 1

1 points

Jan 26, 2011 6:32 PM in response to JMWhitt

I have also found another workaround. I have not tried the smcFanControl yet but I went under the system preferences and went to energy saver and scheduled my computer to shutdown every week on the same day and then start back up about 15 min later. It's not a fix but definitely a way to get around it.

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