Fans Blowing After Replacing HDD?

harry*333

macrumors 6502a
Original poster
Jul 24, 2009
505
28
Just finished a bit of work on my parents' iMac(Early 2009 24" 2.66GHz). I replaced the hard drive with a new 2TB hybrid drive and put new thermal paste on the CPU. Reassembled everything and booted from a USB drive to install. Immediately upon powering on the fans began blowing at full. I formatted the new drive and installed Yosemite. Rebooted and still fans are blowing. Looking at Macs Fan Control, only the CPU fan is misbehaving, running at max. I can however manually control the fan. CPU temps are fine at 33°C and do react normally when put under load(I ran a Geekbench test to see).

I've tried rebooting, a PRAM reset, an SMC reset... not sure what to try next ???
 

WilliamG

macrumors G3
Mar 29, 2008
9,113
2,588
Seattle
Just finished a bit of work on my parents' iMac(Early 2009 24" 2.66GHz). I replaced the hard drive with a new 2TB hybrid drive and put new thermal paste on the CPU. Reassembled everything and booted from a USB drive to install. Immediately upon powering on the fans began blowing at full. I formatted the new drive and installed Yosemite. Rebooted and still fans are blowing. Looking at Macs Fan Control, only the CPU fan is misbehaving, running at max. I can however manually control the fan. CPU temps are fine at 33°C and do react normally when put under load(I ran a Geekbench test to see).

I've tried rebooting, a PRAM reset, an SMC reset... not sure what to try next ???
Did you notice a thermal sensor on the original hard drive?
 

WilliamG

macrumors G3
Mar 29, 2008
9,113
2,588
Seattle
Just stuck on the outside
Hm.. Not sure what to tell you. Perhaps someone with more knowledge of that 2009 iMac will tell you more. I know on my late 2009 27", the thermal sensor was an actual plug-in type deal, so I had to short that cable or the fan would run full speed with the replacement drive I put in.

Also, I read this:

"Make sure you reconnect the cable for the thermal display sensor during reassembly. If you don't, the fans will be running at max speed and you might think it is from the drive thermal sensor afterwards (which is an issue some users have and which can be fixed in software)."

From this:

https://www.ifixit.com/Guide/iMac+Intel+24-Inch+EMC+2267+Hard+Drive+Replacement/9028
 

dr.oid

macrumors newbie
Aug 11, 2013
8
0
I think you need a CPU thermal calibration..and recheck the proper thermal sensor positioning of the HDD.
 

Lankyman

macrumors 68020
May 14, 2011
2,054
790
U.K.
Hm.. Not sure what to tell you. Perhaps someone with more knowledge of that 2009 iMac will tell you more. I know on my late 2009 27", the thermal sensor was an actual plug-in type deal, so I had to short that cable or the fan would run full speed with the replacement drive I put in.

Also, I read this:

"Make sure you reconnect the cable for the thermal display sensor during reassembly. If you don't, the fans will be running at max speed and you might think it is from the drive thermal sensor afterwards (which is an issue some users have and which can be fixed in software)."

From this:

https://www.ifixit.com/Guide/iMac+Intel+24-Inch+EMC+2267+Hard+Drive+Replacement/9028
Shorting out the sensor is such a dangerous trick if you value the long term life of your Mac and should be actively discouraged. I wouldn't use fan control either on my iMac.
 
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WilliamG

macrumors G3
Mar 29, 2008
9,113
2,588
Seattle
Shorting out the sensor is such a dangerous trick if you value the long term life of your Mac and should be actively discouraged. I wouldn't use fan control either on my iMac.
No it's not dangerous. Many of us have done this and to my knowledge it's been 100% successful for all. Google it. :) It's not like you're sticking a knife into fan blades to stop them spinning - you're just disabling a hard drive temperature sensor. :)
 

Lankyman

macrumors 68020
May 14, 2011
2,054
790
U.K.
No it's not dangerous. Many of us have done this and to my knowledge it's been 100% successful for all. Google it. :) It's not like you're sticking a knife into fan blades to stop them spinning - you're just disabling a hard drive temperature sensor. :)
I have Googled it and having done so decided it is not something I would do to any iMac I own. There are many references to the fact that using software to control the fans is not really up to the job and is likely to shorten the life of components.

To spend all that money on an iMac and then skimp on a temp sensor is akin to the economics of the mad house. Only last week I put an SSD in my iMac as an addition to the HDD. I do however have the temp sensor to hand (courtesy of OWC) should I decide to replace the HDD at some future point.

If I don't use it I can sell it. Have you ever heard the saying 'penny wise and pound foolish'?
 
Last edited:

WilliamG

macrumors G3
Mar 29, 2008
9,113
2,588
Seattle
I have Googled it and having done so decided it is not something I would do to any iMac I own. There are many references to the fact that using software to control the fans is not really up to the job and is likely to shorten the life of components.

To spend all that money on an iMac and then skimp on a temp sensor is akin to the economics of the mad house. Only last week I put an SSD in my iMac as an addition to the HDD. I do however have the temp sensor to hand (courtesy of OWC) should I decided to replace the HDD at some future point.

If I don't use it and I can sell it. Have you ever heard the saying 'penny wise and pound foolish'?
There's no skimping when there was no other reliable solution on the 2009 27" iMac. This wasn't a software fix. This was a hardware fix. I hardly think disabling a sensor reliably was pound foolish. To me, spending any money on an unnecessary sensor for an SSD was just as you describe. But to each his own.
 

aliensporebomb

macrumors 68000
Jun 19, 2005
1,844
223
Minneapolis, MN, USA, Urth
I seem to remember this was related to the fact that Apple was expecting the exact same drive to replace the original in any repair and any deviation made the fans ramp up like that. I don't know if iStat Menus would let you override the Apple requirement for an exact replacement in the unit (it's kind of a dumb requirement but may be related to 'larger drives generate more heat so we need to encourage them to keep it below a certain size').
 

harry*333

macrumors 6502a
Original poster
Jul 24, 2009
505
28
I seem to remember this was related to the fact that Apple was expecting the exact same drive to replace the original in any repair and any deviation made the fans ramp up like that. I don't know if iStat Menus would let you override the Apple requirement for an exact replacement in the unit (it's kind of a dumb requirement but may be related to 'larger drives generate more heat so we need to encourage them to keep it below a certain size').
Hmmm, haven't heard of this before but its plausible

Why did you put new thermal paste on the CPU?
Just to give the computer a quick refresh. At least in my experiences Apple has never been good with thermal paste. There's often either too much or too little and whatever stuff they're using degrades over time(it crumbles when the heatsink is removed).
 

vkd

macrumors 6502a
Sep 10, 2012
915
313
Don't bother messing about with hardware sensors. I swapped the HD recently in my 2011 iMac and same thing, fans blowing full speed upon boot.

Solution:
Download and install freeware Macs Fan Control from http://www.crystalidea.com/products?ref=fancontrol_mac. Immediately upon installation fans will be silenced. The software works using the SMART parameters of the drive.

Works for ANY Apple computer.
 

Lankyman

macrumors 68020
May 14, 2011
2,054
790
U.K.
Don't bother messing about with hardware sensors. I swapped the HD recently in my 2011 iMac and same thing, fans blowing full speed upon boot.

Solution:
Download and install freeware Macs Fan Control from http://www.crystalidea.com/products?ref=fancontrol_mac. Immediately upon installation fans will be silenced. The software works using the SMART parameters of the drive.

Works for ANY Apple computer.
The obvious question then is why don't Apple use a software solution given it's so good. This is a classic reason why you shouldn't believe everything you read on the Internet.
 

vkd

macrumors 6502a
Sep 10, 2012
915
313
The obvious question then is why don't Apple use a software solution given it's so good. This is a classic reason why you shouldn't believe everything you read on the Internet.
Instead of sitting there in the darkness of ignorance and throwing out unjustified negative commentaries, why not test what you are questioning FIRST and then comment. That way there would be a basis for your comment, whereas as it stands your opinion is absolutely and completely worthless. Thanks anyway.
 

Lankyman

macrumors 68020
May 14, 2011
2,054
790
U.K.
Instead of sitting there in the darkness of ignorance and throwing out unjustified negative commentaries, why not test what you are questioning FIRST and then comment. That way there would be a basis for your comment, whereas as it stands your opinion is absolutely and completely worthless. Thanks anyway.
It is no more or less worthless than yours, or do you maintain that anyone whose view isn't your view hasn't got a view worth listening to?

I have got the app you refer to, I did try it and that is why I purchased the correct piece of hardware from OWC. Tip - try brushing up on your debating skills.
 

vkd

macrumors 6502a
Sep 10, 2012
915
313
Sorry but I call you out as a liar and a cheat. You are offensive and I have reported you to the admin.
 

AppleNewton

macrumors 68000
Apr 3, 2007
1,697
84
1 Finite Place
try reseating the thermal sensor cable to the logic board. thermal paste replacement isn't always necessary, but you may need to reseat the cpu thermal cable (if i recall on this model there is one). and reseat any optical drive thermal sensor cable as well.

the display also had a sensor cable, so comes down to possible reseating all cables and trying again.
could be the HDD just isn't compatible, not sure how beneficial these hybrid judges are...but seem to be iffy
 
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