Sounds like Fan running too fast.

[richbatsford]

hi Folks

Hope you can help. it sounds as tho the fan is running too fast on my imac. This has happened a few times before and Ive resolved it by resetting the SMC. I tried that several times this time around, but no change.

I downloaded the free trial of iStat which is showing the CPU (or the fan of the CPU?) is running at over 4000 RPM. I live in Australia, but today is a cool day!

Is there anything else I can do to fix or investigate the problem (I dont have any technical knowledge beyond user level) or will I need to take it in to a store?

I havent made any changes to the hardware or installed any new apps recently, the problem just seemed to come out of the blue.

many thanks, Rich

 

[DeltaMac]

Can you tell us which iMac you have?
As it has a ODD (Optical drive) fan, I assume it is a 2011 or older?

The thermal compound, which makes the heat sinks work more efficiently, can harden over time, and lose effectiveness.
The temperature, from the CPU in your situation, goes up to some point, and the fan works harder to keep the CPU cool.
If your iMac has been in active use for 7 years or so, you may need to clean out the vents, and other areas that allow cooling air inside the iMac. You MAY also need to re-apply the thermal compound. It's quite a job, but there's a few sites where you can find steps for opening up your iMac. Cleaning dust out is simply looking for areas that are coated, and cleaning. You can spend some time with a "can-o-air" and do quite a lot.
example:

Open up your iMac? (includes steps for a 2010 to replace the heatsink on a 2010 21.5-inch iMac)
https://www.ifixit.com/Guide/iMac+Intel+21.5-Inch+EMC+2389+CPU+Heat+Sink+Replacement/6268

 

[richbatsford]

Hi DeltaMac

many thanks for your reply. i switched the machine back on to check the year (you're right its mid-2011) and low and behold the fan is now running normally. Could be just because its had time to cool I suppose? Since I restarted it about an hour ago, the CPU heatsink has been gradually rising (currently up to 52 degrees) with the CPU fan stable at around 1000 RPM, so perhaps it was an SMC issue after all?

Meanwhile I noticed the Hard Drive temperature is listed as 52 degrees, with the blue 'status bar' completely filled in. Not sure if thats something I should be concerned about .. the hard drive fan is operating around 1100 RPM.

warm wishes

Rich

 

[Darmok N Jalad]

You can also use Macs Fan Control, and it will help you monitor fan speeds and system temps. You’ll also be able to control fan speeds there.

I suspect you may have dust build up inside, which will make the fan work harder. Just looking at your temps, the CPU seems on the high side if that is at idle. That HDD temp seems really high as well.

Did you let the machine idle for a while before taking those readings, and do you have anything running in the background that might be causing CPU load?

 

[h9826790]

I suspect the power board sensor causing the issue (working intermittently). When there is lack of data, the associated fan will work to 100% to avoid possible overheat. Your fan run at high speed actually means SMC is working as expected.

I believe when you perform the SMC reset in the past, you actually reset the sensors, not really the SMC. That's why it can fix the issue (when the sensors are successfully reset).

 

[richbatsford]

You can also use Macs Fan Control, and it will help you monitor fan speeds and system temps. You’ll also be able to control fan speeds there.

I suspect you may have dust build up inside, which will make the fan work harder. Just looking at your temps, the CPU seems on the high side if that is at idle. That HDD temp seems really high as well.

Did you let the machine idle for a while before taking those readings, and do you have anything running in the background that might be causing CPU load?

thanks for the tip on the fan controller. My last screen shot with 52 degrees on the hard drive was after an hour of intense use (running Logic Pro X and a RAM hungry virtual piano). Currently its 48 degrees after an hour of internet browsing and netflix. I googled the safe operating temp of the processor and from this post on the Intel site it looks like i might be in the clear, but Ill keep an eye on it.

Darmok and Jalad on the ocean

Rich
[doublepost=1517371567][/doublepost]

I suspect the power board sensor causing the issue (working intermittently). When there is lack of data, the associated fan will work to 100% to avoid possible overheat. You fan run at high speed actually means SMC is working as expected.
View attachment 749190
I believe when you perform the SMC reset in the past, you actually reset the sensors, not really the SMC. That's why it can it the issue (when the sensors are successfully reset).

So the lack of Powerboard data would make the CPU fan run like that? Ok, thanks will keep an eye on that.

cheers

Rich

 

[Darmok N Jalad]

thanks for the tip on the fan controller. My last screen shot with 52 degrees on the hard drive was after an hour of intense use (running Logic Pro X and a RAM hungry virtual piano). Currently its 48 degrees after an hour of internet browsing and netflix. I googled the safe operating temp of the processor and from this post on the Intel site it looks like i might be in the clear, but Ill keep an eye on it.

Darmok and Jalad on the ocean

Rich
[doublepost=1517371567][/doublepost]

So the lack of Powerboard data would make the CPU fan run like that? Ok, thanks will keep an eye on that.

cheers

Rich

Yeah, the CPU temp can really range from near room temp at idle all the way up to the 60s under load, depending on the cooling solution. Modern CPUs will throttle down if they reach critical temps. I believe the system will shut down if it gets too bad, like the cooling system completely failing.

 

[richbatsford]

thanks, yeah its showing 52 degrees at the moment and the HDD fan hasn't budged off of 1150 RPM, so presumably that means its an acceptable level.

 

[dawgs4apple]

Hi there, I have a question about my MacBook pro's running CPU temp as well. For no good reason the other day my laptop's cpu got up to 90+C while literally just running chrome and got extremely slow. I installed mac
fan controls to monitor/manage and noticed that until I selected any inputs my fans weren't running at all and were letting the insides cook. A few days later now my laptop can't seem to run without the cpu wanting to shoot up to 80-90+C on the regular. Any suggestions?

 

[DeltaMac]

Which MBPro do you have? How old is it?

Chrome is still known as a big-time memory hog, so it shouldn't surprise you about using high CPU, which would then translate to high fan speed, until you quit Chrome. The temps should drop dramatically then.
You COULD use mac fans control to, well, control the fans, give them a boost for better cooling. They'll get a bit noisy, but it's for cooling.

If your MBPro has a few years of age, the heat sink (thermal) compound can be getting hard, losing efficiency, allowing your CPU to bump up in heat. But the fans should run up by about 70 or 75C. You might at least open your MBPro case and checking that the areas around the fans and vents are clear of any dust.

 

[Darmok N Jalad]

Hi there, I have a question about my MacBook pro's running CPU temp as well. For no good reason the other day my laptop's cpu got up to 90+C while literally just running chrome and got extremely slow. I installed mac
fan controls to monitor/manage and noticed that until I selected any inputs my fans weren't running at all and were letting the insides cook. A few days later now my laptop can't seem to run without the cpu wanting to shoot up to 80-90+C on the regular. Any suggestions?

Does it show that your fans are running at all? You might look into resetting the SMC, and also attempt to get the dust cleaned out. Those temps are too high regardless of your usage, and it appears that the CPU is throttling to protect the system form overheating entirely.