iMac fan constantly running, I've tried everything!

EheroDC

macrumors newbie
Original poster
Dec 28, 2012
13
0
Hi,

I have a Mac (21.5-inch, Mid 2010)
Processor: 3.06 GHz Intel Core i3,
Memory: 4 GB 1333 MHz DDR3,
Graphics: ATI Radeon HD 4670 256 MB,
Running Yosemite 10.10.1

The fan is constantly running quite loud. I have never had this problem until recently and it seems to have started doing it for no apparent reason. I haven't changed any settings or done anything recently. In fact, the most recent change was upgrading to Yosemite.

I have tried doing a SMC reset (several times) which didn't change anything. I have tried lots of doing different ways of doing a Apple Hardware/Diagnostics Test and it told me that "The Apple Hardware Test is not compatible with this machine".
I have kept a close look at my Activity Monitor and nothing is spiking, average use is: System 2.75%, User 5.67%, Idle 90.4%
Using smcFanControl I know the fan is running at 29C and average 996rpm. I don't know if those stats are normal or not, but my fan is still making more noise than it ever has.

Please, can somebody help! I have been trying for weeks now with no success. I very worried that using my Mac is going to damage something and I desperately need it for work. Can anybody suggest anything outside of taking it to apple because that is my last resort which is going to cost me a lot of money

Thank you in advance for your help
 
Last edited:

maflynn

Moderator
Staff member
May 3, 2009
66,390
33,010
Boston
Sounds like the temperature sensor or perhaps that cable is discounted. As SBG asked, did you open it up for any reason?

I did something similar to my Mini, I replaced the hard drive with an SSD, and knocked the cable out of the connector. When I got it all together, the fans were blasting full speed. I had to take it apart and make sure all the connections were tight (they weren't)
 

tyche

macrumors 6502
Jul 30, 2010
411
62
Using smcFanControl I know the fan is running at 29C and average 996rpm. I don't know if those stats are normal or not, but my fan is still making more noise than it ever has.
29C is very cool and 996 rpm is basically as low as you can go and will make no noise. If you're hearing fans blasting really loud that is close to 5,000 rpm.

So smcFanControl is not reading correctly. Sounds like something is broke causing the iMac to max the fans but at the same time report normal values.

Maybe someone can suggest some other monitoring tools perhaps iStat (free version) to see if it can detect abnormalities or SMART errors.
 

EheroDC

macrumors newbie
Original poster
Dec 28, 2012
13
0
29C is very cool and 996 rpm is basically as low as you can go and will make no noise. If you're hearing fans blasting really loud that is close to 5,000 rpm.

So smcFanControl is not reading correctly. Sounds like something is broke causing the iMac to max the fans but at the same time report normal values.

Maybe someone can suggest some other monitoring tools perhaps iStat (free version) to see if it can detect abnormalities or SMART errors.
Through iStat I have found out its my CPU fan that is running at around 4000rpm. I'm guessing that is what is making the noise. Any advice?
 

joe-h2o

macrumors 6502a
Jun 24, 2012
997
445
1000 rpm is around the base speed for the fan - the SMC won't let it run slower than this under normal circumstances, so if it's making a lot of noise then it could be a faulty bearing.

At 1000 rpm (assuming the reading is accurate), the fan should be near silent.

Take it to Apple and have them look at it if possible - you may be able to get them to replace it for you.
 

rigormortis

macrumors 68000
Jun 11, 2009
1,813
229
you said smc is reset.

turn off the computer
unplug it
make sure smc is reset by holding down the power button for 5 seconds, forget what apple says about waiting 15 seconds, that should guarantee that the smc is reset

its been a while since i did this, i might be wrong

like SandboxGeneral and maflynn says it could be a lose wire. or you installed a hard disk without a sensor wire.

but if you run apple hardware test in extended test , it should tell you that there is something wrong with the fans or sensor, it will spit out an error code if there is something wrong with the fans/temp wires.
support.apple.com/en-us/HT201257


if i am wrong about a.h.t. then you need to go to the genius bar and use genius bar diagnosis test to check the fans and temperature sensors, last time i ran the genius bar test it made it look like my mac book air had more then 10 temp sensors.

other then that i just don't know. reinstall os x??? reset pram???

i asked the genius over there once what was the difference between apple hard ware test and genius diagnostics, he said nothing at all. it had no other functionality
 

EheroDC

macrumors newbie
Original poster
Dec 28, 2012
13
0
In activity monitor, do you have any processes using the CPU in excess?
Biggest CPU % is Dropbox at around 14%. Safari and Activity Monitor itself pop up, but thats about it.

By the sounds of it, do you reckon its a case of needing to take it in to be looked at?
 

SandboxGeneral

Moderator emeritus
Sep 8, 2010
26,072
9,261
Detroit
Biggest CPU % is Dropbox at around 14%. Safari and Activity Monitor itself pop up, but thats about it.

By the sounds of it, do you reckon its a case of needing to take it in to be looked at?
Well, if you don't have massive CPU utilization and have never opened it up to swap out the HDD, then yes, I'd say take it in. There could possibly be a blown capacitor causing the fan to spin up like that, or something else.
 

rigormortis

macrumors 68000
Jun 11, 2009
1,813
229
oooh
yeah i didn't see that you tried a.h.t. already

yeah i had the same problem too on my mac mini. they changed internet hardware test so it no longer runs on 2010 machines!!!!


you need your original disks that came with the computer, and press and hold the D key on the disk that says "please insert this disk and hold down the d key" hahaha

that will test your fans/sensors

i tried D, option D and whatever D during boot to get internet diags and i had the same problem, and it won't work and you need your original disks
 

Kemogeden

macrumors newbie
Feb 22, 2017
3
1
Hi,

I have a Mac (21.5-inch, Mid 2010)
Processor: 3.06 GHz Intel Core i3,
Memory: 4 GB 1333 MHz DDR3,
Graphics: ATI Radeon HD 4670 256 MB,
Running Yosemite 10.10.1

The fan is constantly running quite loud. I have never had this problem until recently and it seems to have started doing it for no apparent reason. I haven't changed any settings or done anything recently. In fact, the most recent change was upgrading to Yosemite.

I have tried doing a SMC reset (several times) which didn't change anything. I have tried lots of doing different ways of doing a Apple Hardware/Diagnostics Test and it told me that "The Apple Hardware Test is not compatible with this machine".
I have kept a close look at my Activity Monitor and nothing is spiking, average use is: System 2.75%, User 5.67%, Idle 90.4%
Using smcFanControl I know the fan is running at 29C and average 996rpm. I don't know if those stats are normal or not, but my fan is still making more noise than it ever has.

Please, can somebody help! I have been trying for weeks now with no success. I very worried that using my Mac is going to damage something and I desperately need it for work. Can anybody suggest anything outside of taking it to apple because that is my last resort which is going to cost me a lot of money

Thank you in advance for your help

After 5 years of this problem, even taking it in to the Dealership and them saying it was something wrong with the logic board, and because I had no AppleCare I either had to live with it or buy a new computer, I finally fixed it! I tried SMC Fan Control, HDD Fan Control, and nothing worked. I'll get to the point, but I would like to say had I not returned to this ongoing problem while fixing other things it wouldn't have worked. What worked for me, was the Macs Fan Control program! It runs now at a quiet temp and it is perfect! Thanks.
 
Last edited:
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black71

macrumors newbie
Feb 27, 2017
2
0
After 5 years of this problem, even taking it in to the Dealership and them saying it was something wrong with the logic board, and because I had no AppleCare I either had to live with it or buy a new computer, I finally fixed it! I tried SMC Fan Control, HDD Fan Control, and nothing worked. I'll get to the point, but I would like to say had I not returned to this ongoing problem while fixing other things it wouldn't have worked. What worked for me, was the Macs Fan Control program! It runs now at a quite temp and it is perfect! Thanks.

Kemogeden!!! I could kiss your bald head. I've been working on this forever and no other solution worked. I just downloaded Macs Fan Control and ---- IT WORKED!!!! Thank you so much. I can't tell you how much I appreciate it. This has been bugging me to no end.
 

Kemogeden

macrumors newbie
Feb 22, 2017
3
1
Kemogeden!!! I could kiss your bald head. I've been working on this forever and no other solution worked. I just downloaded Macs Fan Control and ---- IT WORKED!!!! Thank you so much. I can't tell you how much I appreciate it. This has been bugging me to no end.
Thanks man. I run it using the temp of the Airport Card. Running at 1792 rpm right now; much better than 3600! Cheers.
 

Samuelsan2001

macrumors 604
Oct 24, 2013
7,694
2,118
Thanks man. I run it using the temp of the Airport Card. Running at 1792 rpm right now; much better than 3600! Cheers.
Do keep an eye on the temps though at 7 years old it could well be that the thermal paste has degraded and the fans were spinning up to keep the GPU cool you will now be risking damaging the GPU if you force it to be slower when it needs that cooling.
 
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black71

macrumors newbie
Feb 27, 2017
2
0
Do keep an eye on the temps though at 7 years old it could well be that the thermal paste has degraded and the fans were spinning up to keep the GPU cool you will now be risking damaging the GPU if you force it to be slower when it needs that cooling.
Excellent point. Will keep an eye on it. Still working perfectly.
 

mlaun

macrumors newbie
May 18, 2017
1
0
After 5 years of this problem, even taking it in to the Dealership and them saying it was something wrong with the logic board, and because I had no AppleCare I either had to live with it or buy a new computer, I finally fixed it! I tried SMC Fan Control, HDD Fan Control, and nothing worked. I'll get to the point, but I would like to say had I not returned to this ongoing problem while fixing other things it wouldn't have worked. What worked for me, was the Macs Fan Control program! It runs now at a quite temp and it is perfect! Thanks.
You're a Godsend. Thank you for posting this. I know the cause for me is a failed internal HD. I don't care because I'm using an external SDD for my system drive. No I feel I can sleep easier tonight :)
 

Kemogeden

macrumors newbie
Feb 22, 2017
3
1
You're a Godsend. Thank you for posting this. I know the cause for me is a failed internal HD. I don't care because I'm using an external SDD for my system drive. No I feel I can sleep easier tonight :)
My pleasure!
 

Southern Dad

macrumors 68000
May 23, 2010
1,532
557
Shady Dale, Georgia
This has been driving me crazy on my iMac 27" for quite a while. Kemogeden's solution works. I was also able to tell the problem is the ODD fan. A quick change of which sensor should control that fan and all is good now.
 

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