Q: 27" iMac Hard Drive Fan Problem

Check here for HDD sensors:

http://www.macpartsonline.com/catalogsearch/result/?q=optical+temp+sensor+cable& x=0&y=0

I'm still trying to find the sensor cable for 27" 2011 iMac     no luck so far except for gravis.de which is not selling them in the USA.

you can order it online..

I took my imac27 i5 to one store to fix and he replaced it with WD 1TB HDD but the fan noise appeard, then I took it to some one installed this cable for me 922-9229 Optical Temp Sensor Cable -  27 inch Core2Duo - Intel i5 - i7 iMac Late 2009 A1312

Now I'm using it for almost 6 months without any noise

You can keep searching...  the 2011 iMac doesn't use a sensor...

jyavenardis right my imac is 2009 not 2011

... I was answering to Xenophyte who wrote "

I'm still trying to find the sensor cable for 27" 2011 iMac     no luck so far except for gravis.de which is not selling them in the USA."

so obviously, he's going to have a hard time finding a cable that doesn't exist.

2011 iMac doesn't use a hard drive sensor?  Oh this is news to me - I don't have it apart yet, but from other forums it sounded like there was a sensor.  Thanks for explaining.

~ X

2011 iMacs use drives a special firmware with their hard drives, so OS/firmware can read the temperature directly from the hard drive.

Now, if you plug a non-apple drive, the fans will speed up like crazy.

There are only 2 ways to solve this: use an application to control the fans speed, or short two pins on the SATA cable.

In both cases, the fan speed will never change on their own, and you need to be careful to manually set their speed so they do what they are supposed to do: cool down the mac.

The advantage of shortening the two pins on the SATA cable, is that you mac won't fail the hardware test.

Thanks for the tip, added search terms including "short" and now I found:

http://www.anandtech.com/show/4340/27inch-apple-imac-review-2011/5

referencing the real meaty article at:

http://www.hardmac.com/news/2011/05/14/it-is-currently-impossible-to-replace-the -hard-drive-of-the-2011-imac

"It is the solution provided by Apple on the models coming with an SSD: short-circuit pins 2 and 7 on the power supply cable.

...

[On the] 2011 model ... the [disk temperature?] information now goes through pin 11 of the power supply connector, which is normally used to light-up a LED during disk activity. In prodder to change the use of that pin, a specific firmware was needed, which explains the reason that only disks sold by Apple in the iMac don't have any problem."

I am a MAc user for over 20 years. I have an Imac 20", early 2008, 2,66 GHz Intel core 2 duo, 4 GB 800 MHz DDR2 SDRAM, Graphic ATI radeon HD 2600 Pro 256 Mb with Lion Operating system.

The problem I have is that the HD fan goes crazy at certain times, using iPhoto, with screen protector, using Top SItes of Safari...They all have in common the use of the graphic card. After putting the computer to sleep, HD revs drop from 6000 thar had reached and working properly. I sent the computer to an Appple service twice and failed to find fault. I have changed the leoaprd operating systeim to Snow Leopard and now a Lion without result. I have rest PRAM, PMU, Preferentes, Onyx...

Any idea what could be solve the problem ?

Do you think the HDD fan control program would solve the problem?.

Thanks.

From what you describe, it seems it's owing it's job: cooling when thevimac is heating up.. It's definitely not something you want to mess up with. You don't want to use a tool that will reduce necessary cooling.

As I read in a previous message of yours, you mention that if there is a change in the HD fans "will speed up like crazy". I think you are wrong: my original 250GB Apple drive passed away and the Apple distributor installed a 750GB of the "hated" Samsung that works very well in all senses: no revs speeding up, no overheating, no nothing.

MY problem is that I am a BOINC user and I have two analytical tools installed, SETI and ROSETTA, which make the CPU working at full steam 100% of the time. I saw the CPU's temp to go over 70ºC and I decided to do something. GPU's temp is always at reasonable values around or below 50ºC. I installed smcFanControl that allows me to set up the exac revolutions for the three fans: HDD, ODD and CPU and show their respective temperatures, keeping CPU temp around 60-65ºC.

Since then fans work at the speed I setup and I can change the speeds anytime. Super application and it is shareware. If it works, you donate some money.

I read again your message and you referred to a 2011 iMac. I do not know if my solution is applicable to a 2011 Mac but I do no see why not.

I nearly forgot to say I have a iMac 20" early 2008, 4GB RAM, 750GB HD

And the problem was in relation to late 2010 and 2011 iMac (e.g less than 18 months)

now if your iMac had a 250GB hard drive, it's obviously an older model and isn't affected by the issue described...

My message was meant to give ideas: this program is widely available and I assume continues doing its job HELPING TO CONTROL THE FANS OF THE IMAC.

The fact that my comp is older does not disqualify to give ideas that could help.

Thanks

Hello

Thanks for everyone's help on here.

I have the same problem: however after buying HDD fan control the problem returned.

I uninstalled it and am now trying smcFan control but with readings of 46˚c and 999rpm I'm still getting the dreaded fan noise.

However the CPU is running at 3784rpm just with Safari & Terminal open.

I was just wondering if there has been any further success by anyone…?

I have a 27" and am running 10.6.8

iStat is showing it's my CPU fan that is going bonkers (3900) on 2008 iMac. Temps are fine. This happened after the dreaded HD replacement. HDD Fan Control does nothing. I need my fan to slow down(!!), and its not the HD fan, anyway. No, I can't tell you what went wrong during the HD change out? No I don't think I left any cables unconnected, etc. But I got fan noise, constant.

This worked specifically for me (from an archived thread):

"Hooray, I think I found a solution.

Using terminal commands there actually is a way to force smcFanControl to set a tolerable max rpm for the CPU fan.

WARNING:

Be aware that this solution should only be used if you know what you're doing and you are absolutely sure the CPU fan on your iMac is indeed out of control.

Forcing a low max speed on a healthy CPU Fan with fully functioning sensors can seriously damage your Mac. You have been warned.

The solution:

Install smcFanControl

Go to the terminal and use these commands to regain control of your noisy iMac:

/Applications/smcFanControl.app/Contents/Resources/smc -k F2Mx -w 12c0

This will set the CPU Fan to max at 1200 rpm: (Oh yes!)

To revert to standard settings use:

/Applications/smcFanControl.app/Contents/Resources/smc -k F2Mx -w 3cf0

This will set CPU Fan to max at the default 3900 rpms

You might have noticed that the last 4 digits are the fan speed (in hexidecimal)

Other fan speeds you can try:

1100rpm = 1130

1500rpm = 1770

3900rpm = 3cf0

Now all I need is a way to make the setting permanent. Anyone know how to run the above terminal command automatically on bootup?"

But like he leaves off, anytime you sleep, power down, etc. One needs to run it in terminal again. Anyone automate this. A developer write an app for this(throttling the fan down - yeah I know, dangerous, but I do not have a temperature problem), please?