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Razorbeam Grrl Level 1 Level 1

I have a 2007 iMac that for some reason the fans won't speed up above idle and so if it's put to heavy use eventually it will overheat and shutdown. It was a while before I had installed software that measured temperatures of devices or fan speeds inside the iMac and then determine what was happening and that indeed the iMac would shut off when the power supply got too hot.


Then I found some of these apps that let you control the fan speed manually or customize the threshold and with some of these I was able to speed the fans up. The one I chose as the best was Derman's version of Fan Control, a control panel which is automatic and effectively keeps all the temperatures normal and has been my solution to the problem. Many people seem to like SmcFanControl for some reason but I don't because it's crude and  totally manual in setting the base fan speed which keeps the fan running higher than normal all the time but doesn't help much to cool if the iMac gets really hot unless you manually speed up the fan more.


The whole thing baffles me. Why can this control panel speed up and control the fans just fine and effectively cool the iMac but left to it's default control it does nothing and allows the iMac to overheat? And has anyone had this problem and found a way to fix it?

iMac (20-inch Mid 2007), OS X Mountain Lion (10.8.1), 4GB RAM, 1TB HD
  • den.thed Level 7 Level 7

    When was the last time you seriously vacuumed out the the air intakes (the grill work on the bottom, the small vent behind the stand and upper exhaust slots) to ensure that you have a good clean air flow? Or even better, taken it into service for a full cleaning of the air passageways, fans and heat sinks?

  • Razorbeam Grrl Level 1 Level 1

    This doesn't address the problem of the fans not speeding up when it's hot at all.


    But if you must know it's very clean inside and operates in a house that has high end air purifiers and is nearly dust free. And I have had it apart to change the hard disk and there was only a small amount of very fine dust to clean out and nothing more.

  • RRFS Level 5 Level 5

    I believe that MtLion works older systems harder because it is resource hungry and that the newer versions of the OSs allow for higher operational temps before the fans ramp up. Here is a Widget to check your temps and a comparison temp list. To keep your temps lower than the factory settings you will need to run an aftermarket fan control App.




    Try a SMC Reset just in case that has messed up.



    • Shut down the computer.
    • Unplug the computer's power cord and ALL peripherals.
    • Wait 15 seconds.
    • Attach the computers power cable.
    • Wait another 5 seconds and press the power button to turn on the computer.
    • It is the 5 second timing that initiates the reset.
  • Razorbeam Grrl Level 1 Level 1

    The problem is that the fans never speed up at all and has nothing to do with how hot the OS makes it. And as I said I have to run Fan Control to get automatic fan cooling to work and wonder why the iMac's default fan control won't do it when an app has no trouble doing it. I've already tried resetting the SMC and the iMac has the latest firmware but still the fans only run at 1200 RPM and never change when no fan app is being used.

  • den.thed Level 7 Level 7

    Razorbeam Grrl wrote:


    This doesn't address the problem of the fans not speeding up when it's hot at all.


    I'm not sure why Apple has the thresholds set up so high, perhaps to maintain a quieter all-in-one system than it's competitors. Problem is, that eventually it comes at a price and after a few years (5+ in your case) the hardware begins to suffer.


    I am with you and also believe that cooler hardware will last longer..! That's why I've been using SMCFanControl on my 2006 iMac for over 6 years, which seems to have paid off. I'm also using Fan Control on my 2010 Mac Mini in hopes that it too will last as long or longer than my iMac.


    Razorbeam Grrl wrote:


    But if you must know it's very clean inside and operates in a house that has high end air purifiers and is nearly dust free. And I have had it apart to change the hard disk and there was only a small amount of very fine dust to clean out and nothing more.


    I was just checking, not many folks think to even clean the dust off the intake grills regularly must less the insides.

  • Razorbeam Grrl Level 1 Level 1

    If any of my Macs get dirty inside I'll carefully take them apart and vacuum and blow out the filth. I make sure that I observe ESD practices with ground straps.


    The thing is that the iMac fans never speed up at all and it overheats and will shutdown eventually. My MacBook Pro fans act normal and speed up when it gets hot.


    I initially used SmcFanControl but it still allowed the iMac to get too hot since it's only a simple manual adjustment and it keeps the fans running at a constant higher speed all the time which I don't like as far as fan wear and sucking in more dust goes. but the Derman version of Fan Control has an iMac version that works beautifully and idles the fans low and cycles them up as needed to keep it cool. You might want to try it on your iMac and get rid of SmcFanControl.


    I have the lower and upper thresholds set at 45° and 65° and the fan speed lowest and the iMac runs very cool and rarely do I hear the fans spooling up. What I've noticed is that the iMac power supply is what gets overtemperature before anything ese does and so with the lower threshold set to 45° that nudges the fans up which keeps the CPU in a very cool 50's* range which compensates at keeping the power supply in a happy low 60's° range.

  • MichelPM Level 6 Level 6

    I'll chime in on this.

    I took a look at Derman Fan Control. Don't like it. Too much extra complication for a simple fan control task.

    I do not care about completely quiet operation.

    I'll live with some minimum level of fan noise to obtain a cooler running iMac.

    Compared to my old G4 MDD Wind Tunnel model, even with some noticeable fan noise, my iMac is still much quieter.

    I do not consider 50 to 60 degrees C very cool for any component. 122-140 degrees Fahrenheit is not very cool.

    Plus,,the GPU heat sink and diode and the PSU without any fan control was running between 145 and 159 degrees Fahrenheit. These temps IMO, are completely unacceptable.

    I run SMC fan control within a 1600-1800 rpm range.  True, the fans run at this constant speed, but the fans are running only at 40%-50% faster rate. Hardly speeds that would prematurely burn the fans up.

    This range also keeps my iMacs fans from sucking in excessive lint, dust and dirt.

    With the fans running in this range and using Photoshop, my PSU temps have dropped to 135-140 or so degrees. At idle, the PSU rests at a comfortable 132-135 degrees Fahrenheit. The CPU temp has dropped to around 110-115 degrees Fahrenheit. At idle or less intensive applications, the CPU temps are between 95-102 degrees or so Fahrenheit.

    With SMC Fan control my HD temps have dropped from almost 130degrees Fahrenheit  to anywhere from 102-120 degrees Fahnrenheit.

    The number one cause of computer component failure is heat. The three main things, that I noticed with the newer iMacs, that can fail due to heat, CPU, GPU and the HD and sometimes,,the whoe logic board.

    Any one or combinations of the above can render the iMac useless.

    I want my iMac to run as cool as I can possibly and acceptably can get it to.

    Just adding my 2 pence for what it' worth.

  • den.thed Level 7 Level 7

    Adding one last cent. When you look at things from any manufactures perspective, isn't it a bad marketing strategy to built anything that lasts longer than 2 or 3 years?  

  • RRFS Level 5 Level 5

    You really haven't told us whay your subjective view of "too hot" actually is. I agree with MichelPM. The Apple idea of letting the components get hot for the sake of quiet is ridiculous. I too find that a bit more speed provided by the SMC Fan Control helps the entire system stay cooler and when running demanding applications their base speed should be upped just because of the known intended load. I know that the manufacturers test their components in LABS and say they can withstand these higher temps (70-90 deg C) but long term the whole system will suffer under that kind of heat load. Personally I think that has been part of the problem so many owners of the 27" iMacs experienced with the LCD Panels outgassing and causing "smudges" inside the panels themselves.

    All that being said, if your power supply is getting hot enough to self limit by shutting down, I would suspect there is a problem with the power supply itself. It could be electrical leakage through some component causing an excessive power draw making it work harder.

  • Razorbeam Grrl Level 1 Level 1

    Well too hot is when it's temperature gets somewhere above 90° and it shuts down. I've made it obvious that the FANS are what the problem is in that they won't change speed automatically as they are supposed to in order to cool. I'm tryng to see if there is a fix for the fans but so far it's frustrating since everyone ignores what I'm asking for in regards to the obvious fact that the fans aren't speeding up and what a fix for that might be. I mean if I take any computer power supply and slow the fan way down and leave it that way it's going to overheat and that doesn't make the power supply defective it just means that it's not being properly cooled by the fan as is happening in my case.


    The Fan Control panel I use works fine and spools the fans up and down automatically but it would be nice if the iMac would do that by default as it's supposed to. I'd just like to see if anyone knows why it isn't and if it's fixable.

  • MagnusVonMagnum Level 1 Level 1

    As you have already noted, the problem with SMCFanControl is that it only sets a higher minimum speed which leaves the user to have to manually ramp it up (or define a higher preset for various level tasks) when running something that will tax the CPU.  Cooler idle speeds will do little to extend the life of your computer.  My new Quad-Core i7 Mac Mini idles at a cool 110-115 degrees Fahrenheit (yes, that is COOL in computer terms to those that think it's hot because a day in Arizona at that temperature feels very hot). 


    Manual control is better than nothing if you know you're going to play a game or encode a file, but it stinks if you have a batch of files and you leave the room and it finishes and your fan keeps needlessly running at higher speeds (possibly for days if you left on a trip and left a list of videos to convert while you're gone).  I've left feedback on SMCFan's web site, but perhaps having an upper limit is beyond the author's capability?


    Derman's Fan Control has exactly the features needed, but sadly it hasn't been updated since 2007 as far as I can tell (Leopard Era) and thus may not be suitable for a newer Mac running Mountain Lion (the preference pane is also not 64-bit).  iMacs and Macbook Pros all have different fan setups for different equipment and my Mac Mini has its own case fan.  In my case, a Quad i7 will quickly reach 180+ degrees Fahrenheit or hotter when encoding with Handbrake at full speed.  Apple's own fan FINALLY kicks in beyond a smidgen at around 90C/190F, but it doesn't reach near full speed until it gets hotter yet (it seems content to let the CPUs roast at 90C/190F; I think Intel's automatic throttle is at 105C/221F, so perhaps Apple thinks that 90 is perfectly fine.  I'll admit the case isn't super hot or anything, but the concern should be the shelf life of the CPU and other components in the computer, not whether it will run at that temperture for weeks or months or even a year or two. 


    My PowerMac Digital Audio PPC tower (upgraded to 1.8GHz/1.5GB with dual 1.5TB Sata drives and used as a whole house audio/video server for over 6 years on nearly 24/7 and god knows how much before I bought it used in 2006) still works fine (case fan is starting to get a bit noisier, but still functions and the machine was on 24/7/365 for the most part!  It was built in 2001!  That's 11 years with no component failures and over 4 years 24/7 on the 1.5TB drives).  I'd like my new Mac Mini Quad i7 to last at least half that long.


    In short, there aren't many good solutions because no on has bothered (or at least bothered to update) a good fan control for the Mac.  I found a fan control program to run in Windows on my Macbook Pro and it has no configurable options, but automatically ramps at a very good set of default temperatures  and so it's just set to automatically run at startup and forget (I wish I could say the same about OSX; Apple's defaults seem to be set for quiet operation with little thought about longevity).


    I'd gladly pay a few bucks to have a good quality fan control program in OSX that is up-to-date, 64-bit and works fine with my new computer in Mountain Lion.  It's a shame I can't seem to find one to buy.

  • Mi_ka Level 1 Level 1

    I had intermittent shutdowns on my late '09 Macbook Aluminum since Lion came along and the problem continued persistently with Mountain Lion eventhough thermal monitoring programs I installed never reported CPU going over 78 Celsius or so.

    From what I read this is not an uncommon symptom for simliar MB and MBP machines.


    The Fan Controll app solved this for good and I too would happily pay for an official app.


    My belief is that Apple is not very inclined in keeping older machines properly supported for newer and heavier versions of the OSX and particularly with Lion they seem to have chosen the (Microsoftish) path of adding stuff without streamlining what's already written so machines have been having more workload than they should, hence higher working temperature since the fans are reluctant to kick in. They seem to have put there an rpm-temperature map too shy noise wise and they never updated this map later on. With Mountain Lion it seems they simplified things (eventhough memory mangement still seems cr@ppy: I had to finally get 8GB to have my Macbook evade memory shortages when heavy web-surfing) but it was still running hot.

    With an Intel shutdown temperature for my CPU at 105C and maybe a safe limit by Apple at say, 95C, it seems the CPU workload spikes on occasion 10-15 Celsius above what the motherboard measures and so it is not reacting fast enough to avoid shutdown.

    Hence, Fan Control does what Apple should have done for us in the name of proper after sales support...


    (I should have known about Fan Control before my expensive original battery balloned due to constant hot running - grrrr, Apple!)

  • shawnhoefer Level 1 Level 1

    Have you found a solution yet?  I have the same problem.  Upgraded my iMac to 10.7.5 and a 1Tb HDD, now it gets hot and shuts down before the factory fan settings even speed up.  It gets to be real annoying and happening on a more regular basis.  I've cleaned the machine and done all the reset stuff and it's still happening.  Funny thing is I don't hear the fans speed up before it shuts down.  I know the fans area all working because with SMC I can speed them up individually and hear them speed up.  Have installed SMC and as long as I have fan speeds up it has not shut down, but would like a more advanced program.  I tried to load the Derian fan control, but won't work with 10.7.5 .  I like the idea, it just hasn't been updated.





  • MagnusVonMagnum Level 1 Level 1

    This program worked for my 2012 Mac Mini running Mountain Lion (10.8.2 and now 10.8.3)  :


    I believe there is a modified version for iMacs with an extra control for hard drives under "Derman Fan Control"  ( ) but I cannot test it since I don't have an iMac.


    In either case, it lets you set the desired minimum temperature grades and kicks the fans it automatically at the defined curve you set as it gets hotter.  This solves all my issues on both my MBP and Mac Mini since I don't have to worry about changing fan settings ever.  It's all automatic based on the temperature sensors once you set what you want.  I don't know why anyone would EVER want to use SMCFanControl when this is available.  It's night and day better (i.e. automatic versus manual).  SMCFanControl will gladly sit by and let your mac toast itself to oblivion.  Unless you tell it to go to maximum ahead of time, it'll just sit there and do absolutely NOTHING when temperatures go up.

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