Max fan speed recommendation?

Discussion in 'iMac' started by winterquilt, Jun 28, 2014.

  1. winterquilt macrumors regular


    Feb 18, 2008
    I'm not into over clocking, I don't really understand enough about it, but recently I've had to get some software that can control my 27-inch, Mid 2011 iMac's fans (smcFanControl) to up the RPM a little to get it to cool down some, but was warned that too high an RPM over a sustained period of time could burn out the fans!

    Now I don't want to do that and have it around 1300rpm but really need to go higher, so would like to call on the experience of those who know best as how to proceed..

  2. simsaladimbamba

    Nov 28, 2010
    Why would you like to go higher with the fan speeds? Is your Mac getting so hot, that it shuts down to protect it from overheating, on a tight schedule?
    If not, let the fans run at the speeds Mac OS X tells them to run and read the following small guide to learn more about acceptable temperatures and even the limits, and that a Mac, while getting hot, does not overheat, and manual fan speed manipulation is not needed in most cases.

    Those Macs in their heat - a sine of over-heating? - a short story by Mister GGJstudios
  3. winterquilt thread starter macrumors regular


    Feb 18, 2008
    Thanks for your reply.

    I wanted a higher fan speed to cool the case down a little because my computer keeps freezing up and shutting itself down. I thought that it might be because it's summer, the case is so hot, but it did it again and the case was not hot because I forgot I left the fans on around 2000rpm.

    I think now that it might be a software issue with Safari and I don't think it's due to the recent upgrade to Version 7.0.4 (9537.76.4).

    I cannot be sure, but it's so very frustrating. Yes, I have a number of tabs open, but I've had more in the past. I just can't think what it is.

    I've tried repairing permissions and verifying my disk..

    Anyway, I still wanted to know (out of pure curiosity) what the fan limits on an iMac were..
  4. drnebulous macrumors regular


    Apr 27, 2014
    Salford, UK

    This is one of the main reasons I got a mac pro. No messing about. My greatest fear with computer is heat - mainly due to the hard drives but also the general parts such as logic board and cpu (even ram!).
  5. Cubytus macrumors 65816

    Mar 2, 2007
    Safari is a known CPU hog. I did experience the same freezes when my CPU was above 95 degrees for extended periods of time. Just use common sense: a fan spinning at max speed will wear it out faster, as any mechanical device, but also draw more dust inside.
  6. khedden macrumors member

    Jun 18, 2014
    Charleston, SC
  7. Cubytus macrumors 65816

    Mar 2, 2007
    Surprised? I wasn't. Never installed Flash since I reinstalled the OS due to hard drive change. Still, by itself, Safari likes to eat in the CPU.
  8. winterquilt thread starter macrumors regular


    Feb 18, 2008
    Thanks people but I have already implemented, or are aware of these facts, but what I don't know are maximum (tested) fan speeds with the hardware that I have?
  9. GGJstudios macrumors Westmere


    May 16, 2008
    Have you determined that the freezing and shut downs are heat related? It's very likely that it has nothing to do with heat. Heat-related shut downs are relatively rare.

    If you're not already doing so, use iStat Pro (free) or iStat Menus ($16) to get accurate readings of your temps, fan speeds, etc., rather than relying on your sense of touch or sound. A forum member has posted a copy of iStat Pro that has been "tweaked" to enhance compatibility with recent OS X versions. You can download it here.
    The Intel processors used in Macs are designed to automatically shut down to prevent damage if they truly overheat. CPU Tjmax = 105C (221F), GPU Tjmax = 100C (212F) on i3, i5, i7 processors. (Source: Intel)
    Unless there is a rare defect in a Mac, most temps are well within the normal operating range, considering the workload being put on it. Websites with Flash content, games and other multimedia apps will put higher demand on the CPU/GPU, generating more heat. This is normal. If you're constantly putting high demands on your system, such as gaming or other multimedia tasks, expect temps to rise and fans to spin up accordingly. It's just your Mac doing its job to maintain temps within the normal range.
    It is also quite normal for your Mac to become extremely hot to the touch during intensive operations. The aluminum body transfers heat more effectively than other materials used in computer casings, so you will feel the heat more. This doesn't indicate that it's overheating and will not harm the computer to be hot to the touch.
    Your fans are always on when your Mac is on, spinning at a minimum of 2000 rpm (for MBPs) or 1800 rpm (for MBAs, MBs and minis). iMacs have 3 fans with minimum speeds in the 800-1200 range. They will spin faster as needed to keep temps at a safe level. If your fans are spinning up without increased heat, try resetting the SMC. (PRAM/NVRAM has nothing to do with these issues, so resetting it will not help.)
    The intake and exhaust vents are in the back of the computer near the hinge on all Mac notebooks (except the new MBP with retina display, which has intake vents along the sides at the bottom). The iMac vent is a slot on the back near the top of the computer. Make sure the vents remain unblocked to allow your computer to perform at its best. For Flash-related issues:
    Repairing permissions and verifying your disk have nothing to do with fan speeds or temps. The primary furnaces on your Mac are the CPU and GPU, which drive up temps as workload increases.
    If you let your iMac manage itself, you don't have to worry about damage from heat. You don't need 3rd party apps to control fans and you don't need to intervene in the cooling process. Your Mac is designed to manage heat properly, increasing and decreasing fan speed as needed to keep temps at a safe level.
  10. Cubytus macrumors 65816

    Mar 2, 2007
    Don't forget to keep your machine clean on the inside, especially if you never turn it off. Fan speeds dropped dramatically when I had my MB cleaned at the Apple Store. BTW a non-unibody MB has a fan running at a minimum of 2000 rpm, not 1800.
  11. MartinAppleGuy macrumors 68020


    Sep 27, 2013
    What is the temp where you live?
  12. h9826790 macrumors G4


    Apr 3, 2014
    Hong Kong
    For this kind of issue, at least do the followings (in order):

    1) SMC reset
    2) PRAM reset
    3) Boot into recovery partition
    4) repair permission
    5) repair disk
  13. GGJstudios macrumors Westmere


    May 16, 2008
    Of those items, only resetting the SMC can have any effect on fans. The others will have no effect on heat or fan speeds.
  14. h9826790 macrumors G4


    Apr 3, 2014
    Hong Kong
    But his computer keep freezing, all these may help to solve the problem. Also, apart from SMC, other reset / repair may fix some software issue which reduce CPU loading eventually and therefore reduce heat.
  15. Dirtyharry50, Jul 1, 2014
    Last edited: Jul 1, 2014

    Dirtyharry50 macrumors 68000


    May 17, 2012
    As others have noted, fooling with the fans should never be necessary on an iMac. I have the same model as you and have experienced the following heat related failures which thankfully have all been covered by AppleCare:

    LCD panel x 2
    Glass panel that covers the LCD x 2
    DVD drive
    6970m GPU
    All three internal fans were also replaced with the last repairs done.

    So, nobody can tell me a mid-2011 iMac doesn't have issues with heat because mine sure does and it is made exactly the same way and with the same components as any other iMac of this model year and size.

    That said, cranking the fans isn't the answer as it will just burn them out before their natural life expectancy. I would recommend being sure to keep not only the vents in the back clear (a large paperclip works well for this after vacuuming it to be sure they are entirely clear) as well as the vents along the bottom which can be easily removed with a screwdriver. When your machine heats up and you can hear the fans spinning up, try holding your hand close to the upper vents on the rear of your iMac just beneath the top of it. You should feel air flow there. If you do not, that is a major problem you need to attend to in order to avoid damage to components. Even though the CPU and GPU will shut themselves off to avoid melting, that doesn't mean that prolonged exposure to heat for them and the entire interior of your iMac is anything you want to allow to happen. It should always be venting upward and outward via the fans but it won't if airflow is blocked.

    It is my understanding that models since the 2011 now run cooler than the 2011's do and I am glad to hear that. I think the design of the 2011's is at least somewhat flawed based on what I've seen with my own, as much as I love the thing, love OS X, etc. I am hopeful that my next iMac will not keep melting itself the way this one has.

    Sorry to go on so long but that's my experience for what it's worth. It's also why I preach to people about the value of AppleCare. I would have been really screwed without it in this case.

    So in summary, I agree with the suggestion to get a decent utility to report on system temps. I like one called aptly enough, "Temperature Gauge" which provides readouts on every sensor in your iMac and also provides an easy way to see the highest it has gone since the last reboot. In addition to that you can tell it to log the temps in comma separated value format so you can import that data in Numbers or Excel and view it, graph it, etc. It's a great way to have a look at what happens when you run a demanding game for example. You can see how high the temps go. You might be surprised as I was to see that the hottest sensor consistently is not the CPU or GPU at least in my iMac. It is the power supply heat sink generally. The Temperature Gauge is available on the Mac App Store for five bucks and in my opinion is money well spent for any iMac owner. Monitoring the temps periodically can tell you about trouble before stuff starts melting allowing you an opportunity to do something about it before failures happen. I'll be watching my temps now and making sure the vents are clear for openers if I see them starting to rise and otherwise, I'll be calling my friends at AppleCare if the vents are clear and it is still melting again.

    In my own case I do not have high confidence that this machine is going to make it. Why, I don't know since many 2011 iMacs do I presume. Maybe there is some issue with fan control on the logic board? Who knows but Apple owns the problem now after all the work that's been done under AppleCare and fortunately they are very cool about that, no pun intended.

    Good luck and I hope a good cleaning and temp monitoring is all it takes to stabilize your system. If not, it is time to start considering what is going on with Safari in particular since you mention that app.

    Oh, and to answer your original question about fan speeds since I know you were at least curious, the three fans from what I understand should be running within the following ranges in a 2011 iMac:

    ODD 1150 RPM - 2700 RPM
    CPU 940 RPM - 2600 RPM
    HDD 1100 RPM - 5500 RPM

    Although the GPU has a large attached heatsink, it does not have a fan which is why there is no report on one for it. I assume that by design heat is drawn off that heatsink by the ODD fan in particular blowing air by it. I base that on having seen the layout of the components while my system was being repaired each time.

    As a point of reference, with my iMac currently idle other than Safari where I am typing this, all my fans are running at minimum values, the upper case feels warm but not hot and I can feel airflow there. Now, running a game is another story. In fact, I need to do some testing there and create some logs, etc. but haven't gotten to it. I'm not overly concerned but that is only because I have AppleCare and it is Apple's problem if this thing melts again. I am just curious about the extent to which gaming pushes my hardware.

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