Loud Fans / High HDD Temp: iMac 27" mid-2010

Discussion in 'iMac' started by tokyo77, Mar 7, 2012.

  1. tokyo77, Mar 7, 2012
    Last edited: Mar 12, 2012

    tokyo77 macrumors member

    Jul 8, 2008
    Hello everyone,

    For the past couple months or so, (maybe starting around January) the fans on my iMac have been really loud for some reason. It's mainly the fan that's in the bottom left corner, if I put my ear up to it it's really loud, sounds like sitting inside an airplane while it's taking off. I use Bootcamp with Windows 7 Ultimate x64. It happens every time my CPU usage goes over 15%. So basically every time I play a game, even if it's not that intensive especially considering the decent hardware inside this system (i7, 5750) the CPU fan goes up to 4000 RPM, even when I just leave it for a while on the pause screen! I've installed Speedfan to check the temperatures:

    HD0: 58C
    Core 0: 55C
    GPU: 212751C (it must be broken or something)
    Core 1: 53C
    Core 2: 56C
    Core 3: 52C

    Using iStat Nano to read the fan speeds, I'm getting approximately:

    Fan #0: ~1000 rpm
    Fan #1: ~1500 rpm
    Fan #2: ~3500 rpm

    I can control fan 0 and fan 1 speeds but NOT fan 2 speeds. I've tried SMC reset and all that. This problem is pretty surprising for me since my iMac fans have been fine for almost 1.5 years (mid-2010 edition) and now the Fan #2 at the bottom left (at least that's what I think is making the noise) is really loud! (EDIT: I confirmed it's the CPU fan using iStat nano on the OS X side since it gives you the name of the fan)

    Could it be dust or temperature sensor problems? When I expanded the memory from 4GB to 12GB a couple weeks ago I found a lot of small dust ball things on the inside of the memory panel cover (so I couldn't see it when it was actually screwed into the bottom of the iMac) and around the tips of the memory sticks (not inside the slots but around the entrance things). Also my GPU temp readings seem broken according to Speedfan but on iStat they work fine.

    If anyone could help me sort out this issue that would be great. The incessant fan noise is getting on my nerves! I would really appreciate your help.
  2. upbraid macrumors member

    Apr 24, 2011
    are you saying thats your CPU temperature at 0-5% usage? if so that is very high and i suspect it could be a problem with either your thermal paste or cpu fan. most likely the cpu fan since thermal paste would be obvious from the beginning.
  3. tokyo77 thread starter macrumors member

    Jul 8, 2008
    55 degrees C shouldn't be a problem for the cpu though. could it be the HDD? 60 degrees C isn't good for HDD's...

    right now cpu is at 65C. it can get up to 70-75C when i'm playing games.
  4. Spike88, Mar 7, 2012
    Last edited: Mar 7, 2012

    Spike88 macrumors 6502a

    Jan 25, 2010
    Internal temps of 55C HDD / 65C CPU /75C GPU is fine. Although, HDD should be under 58C (re: 50ish C). Fan #2: ~3500 rpm is running way too fast. Any fan above 1,300 RPM can be heard. Fan at 3,500 RPM is really loud. I'd be focusing on the root cause of "Fan #2: ~3500 rpm".

    Have your tried SMC Reset? Have you tried removing all 3rd party fan control software, then performing another SMC reset?
  5. tokyo77, Mar 8, 2012
    Last edited: Mar 12, 2012

    tokyo77 thread starter macrumors member

    Jul 8, 2008
    OK I did another SMC reset. Right now I am using about 10-20% CPU usage and ~2 GB of memory in Mac OS X since I decided not to use Bootcamp (I have two youtube videos open, one playing and one not playing). The temps are (using istat nano so GPU temps arent messed up):

    HD: 58
    CPU: 63
    Ambient: 38
    GPU Diode: 60
    GPU Heatsink: 61
    Mem Controller: 55
    Optical Drive: 51
    Power supply 2: 75

    Optical Drive: 1206 rpm
    Hard Drive: 2136 rpm
    CPU Fan: 3164 rpm

    Fans are already noticeably loud, ~15 minutes after SMC reset and reboot. And the temperatures aren't that high yet. What's going on??? :confused:

    EDIT: 5 minutes later and it's at 3650 rpm...All I did was open up another YouTube video.
  6. Spike88 macrumors 6502a

    Jan 25, 2010
  7. tokyo77 thread starter macrumors member

    Jul 8, 2008
    Sorry for the late reply but I can assure you that the ambient temperature is NOT 100 degrees F. I have a clock with a built in thermometer right next to the iMac to confirm that :) My room temperature is usually about 74 degrees, and 80 max. I also opened up the windows right behind the iMac to cool it down even more.

    Let me rephrase the problem...when I play games and other cpu-intensive stuff, the CPU fan goes absolutely insane, around 4000 RPM which I believe is around the max it will go. It sounds like a jet plane taking off. Now I know from past experience (i.e. before this problem surfaced) and from other iMac owners that the fans shouldn't be up that much. Even when I'm at the pause screen in Mass Effect 2 and my CPU usage is only about 20% the fans speed up to 4000 rpm. It's extremely loud and annoying.
  8. Spike88 macrumors 6502a

    Jan 25, 2010
    As per http://opentoronto.com/calculators/convert_f_to_c_to_f_fahrenheit_to_celsius.php

    38C = 100.4 F.

    Perhaps the internal sensor for Ambient reading is defective? If its defective and showing 100F (or 38C), then it will make its fans RPM go much faster. Faster than needed.

    Perhaps you can run istants nano and check its ambient temp again. Using C scale, is its ambient still within the 3x (38C) range?

  9. tokyo77, Mar 12, 2012
    Last edited: Mar 12, 2012

    tokyo77 thread starter macrumors member

    Jul 8, 2008
    I ran the Apple Hardware Test and got this. Any thoughts?


    Since it looks like a problem with the HDD, could it explain the high hard drive temperatures I talked about earlier?

    EDIT: I also booted back to OS X to take a screenshot. This is after some normal computer usage (copying files, youtube, etc.) then light usage, i.e. did some moderate stuff 30 minutes ago like copying some GB's of files, then pretty light web surfing. As you can see hard drive temp is kinda worrying me. And the fans are noticeable but not loud yet.

  10. Spike88, Mar 13, 2012
    Last edited: Mar 14, 2012

    Spike88 macrumors 6502a

    Jan 25, 2010

    Your iMac's Ambient temp value is still showing as 35C (or 95 F). Is your Ambient temp really that high? Perhaps something is wrong with the Ambient Temp sensor? If at 35C, it will force its FANS to run at 2,400+ RPMs. Remember that any iMac Fan above 1,300 RPM can be heard. Your 2,400+ RPMs must be loud.

    As bozzygti mentioned. Try http://www.hddfancontrol.com/ (even for 1 hour). It it works, then buy the software product. Or, find a way to fix the ambient temp sensor.... For sure.... Your iMac's high ambient temp is sticking out like a lighthouse beam....

    Good luck!!!!
  11. tokyo77 thread starter macrumors member

    Jul 8, 2008
    Unfortunately the hard drive temperature is abnormally high, probably some fan or connection problem especially since there is an error. Also the high ambient temp might be due to built up dust. Anyhow, since it's probably a hardware problem I scheduled a Genius Bar appointment for Saturday.Two questions: will they open up the iMac during the session to take a look inside? Also, will I be able to observe that kind of stuff?
  12. aggri1 macrumors 6502

    Jul 21, 2010

    I've also got a mid-2010, but the i5.

    I regularly see the ambient temperature well above the actual room temperature.

    I also see what looks like nonsense being reported for the GPU temp in Windows (fine with MacOS X). I'm not sure why. Spike88, you indicated that the GPU temp' which tokyo77 showed as "212751C" was actually 75C. Is that based on the 3rd and 2nd last digits of that apparently nonsensical number?

    On a warm day, say 33C, parts of the back of the iMac get so hot that I can't touch them for any length of time. I can't remember what the sensors reported for temperatures, but I didn't worry. I never had loud fans on the iMac (I know that 'loud' is very subjective; I'm comparing them to the screamers on my GF's MacBook Pro 15, which are very loud when e.g. handbraking). In fact, I've only ever noticed the fans at all when I was specifically listening to see whether they were working when I noticed that I couldn't touch the thing. I did hear a faint whirring, and felt a draft of quite warm air out the top.

    Sorry, can't actually help you though. Have 'fun' at the Apple Store.
  13. tokyo77 thread starter macrumors member

    Jul 8, 2008
    aggri1, thanks for sharing. I don't think the second and third digit are related to my actual GPU temperature to be honest, that extremely large number fluctuates a lot and it looks totally random to me.

    It would be nice to know where the ambient temperature sensor actually is inside the iMac. Does anyone know?

    If you are that concerned about the temperatures on your iMac (although my iMac used to do that before the fans started going berserk) then I suggest you try SMC Fan Control for OS X and MacFan for Windows. MacFan uses the command line, so if you're confused then PM me or something.
  14. tokyo77, Mar 16, 2012
    Last edited: Mar 17, 2012

    tokyo77 thread starter macrumors member

    Jul 8, 2008
    OK, apparently there was a post-it note for no reason stuck on the corner of the hot air vent at the back of the top of the iMac. I took it out and I'm not getting 4000+ RPM CPU fan speeds anymore, which is very relieving. I'm only getting up to 3000-4000 RPM CPU speeds occasionally when gaming, and when I stop gaming the fan speed gradually goes down to 1500 RPM.

    However, I reran the Apple Hardware Test and I'm still getting the 4MOT error I described earlier. The 4 digit number at the end fluctuates in the 1300 zone though. HDD temperature is still pretty high, around 57-59 most of the time. This may or may not "slow roast" my HDD over time so I'm concerned.

    Should I go to the Apple store and ask someone about it? My warranty expired so I can't make technical support phone calls to Apple. I don't think I'm going to lug along my 27" iMac; I'm just going to see if the error message/temperature is a significant threat to my system.

    EDIT: I went to the Apple store earlier today to get my iMac checked out finally. The HDD fan was broken, as I had partly suspected. The repair charges were $17.01 for replacing the HDD fan and $39.99 for labor. Not too bad. I'll be getting my iMac back around Thursday. I'll update again then.
  15. tokyo77 thread starter macrumors member

    Jul 8, 2008

    I got my iMac back yesterday, and the hard drive is at reasonable temperatures now, so the fan must have been broken. The temperature goes up to about 55 degrees max, and usually hovers around 50. However, the CPU fan is still very noisy after intense gaming sequences. It was around 3700 rpm just after finishing a mission in mass effect 2. Although it spins down gradually for about 30 minutes down to ~2000 rpm which is pretty quiet. Here are my temps just after gaming, taken from MacFan's temperature reading program, which does not have the GPU temperature glitch that SpeedFan does. However I don't understand what TC0C, TC1C, or TL0P means, can anyone explain? And is the temperature+high CPU fan speed combination normal?

    (the 2700 rpm in the picture should be about 3700 rpm or so)

    Attached Files:

Share This Page