iMac Overheats & Fans Won't Speed up to Cool

Interesting that I have this same issue and to the best of my knowledge have never heard any of the fans running on my iMac (20-inch, Mid 2007).

Recently it has been shutting down 2 or 3 times a day during heavy use and in high ambient temps (80 degrees in the house). I took it apart and cleaned the dust off of the cooling fins and off of the fan blades, which would lead me to believe that the fans do actually run at times. Cleaning it did not change anything as it still was shutting down and very hot to the touch.

Installed Derman's version of Fan Control and the fans immediately came on, ran high speeds for a few minutes and reduced the temps across the board 30-40 degrees F.

I am wondering what the Temp thresholds Apple originally had the fan(s) temperatures set to?

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?

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.

http://islayer.com/apps/istatpro/

http://www.intelmactemp.com/list

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

SMC RESET

http://support.apple.com/kb/HT3964

• 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 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.

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.

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?

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. 😟

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.

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!)

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.

SOMEBODY HELP!!! COME UP WITH A PROGRAM THAT SPEEDS THE FANS UP AS THE MACHINE GETS HOTTER...

HAS ANYONE FOUND A SOLUTION TO THIS???

This program worked for my 2012 Mac Mini running Mountain Lion (10.8.2 and now 10.8.3) : http://fan-control.en.softonic.com/mac

I believe there is a modified version for iMacs with an extra control for hard drives under "Derman Fan Control" ( http://www.derman.com/iMac-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.