iMac 5K Retina Display Late 2015 fan at idle?

I have a late 2014 iMac Retina, and as you say, the fan ticks over at around 1200rpm, but for me it is silent. However, what I have noticed occasionally is that the external backup drives attached to the Mac can create a gentle humming sound that could be confused with that of the computer's fan - especially as the external drives are not immediately visible. Do you have any peripherals attached that the noise could be attributed to?

Thank you so much. This has genuinely changed my life! Just bought the 4K iMac, and it's astonishing how much difference in noise the fans make at about 1200 rpm. As in, even 1150 rpm is much quieter than 1200. 1300 is totally unbearable.

Also, changing the fan speed seems to make very little difference to the temperature. Only when I use all 4 CPUs on full, does 2850 actually make a small difference (72 --> 65) to temperature. But on auto the fans still stay at 1200, as if nothing's happened. Certainly switching between 1000 and 1200 makes no discernible difference when doing most things.

Is 70C temp actually a problem anyway? My Macbook is fanless, and using say google maps in 3D can get it to the high 80s, but it keeps going. No cooling.

Worth getting it looked at under warranty - or perhaps give AppleCare a call. They may have a few suggestions before you have to go through the pain of returning the Mac. Good luck.

Jhua8 wrote:

Paul_31, when you place your ear to the bottom of your iMac, do you hear anything at all? Or is it just silent?

If I place my ear to the lower edge of the front of the Mac or near the stand at the back where the vent is I can hear the gentle whirring sound of the fan, but in the home office I use we have another iMac and various HDs attached that give out a low level of ambient noise so the sound of the Retina Mac just forms part of that noise.

I do recall reading on these forums some long time ago about someone having an iMac that made more noise than he thought it should. The poster finally concluded that if he stood the Mac on a soft cloth on his desk the resonating sound was greatly reduced. Didn't seem like a hi-tech solution but it solved the problem! I doubt this will help you, but thought it worth a mention 🙂

I have the same late-2015 iMac 5k (maxed out) and I can heard the fan, too, spinning at 1200 rpm in a quiet room.

Honestly, I think this is normal.

It is just a gentle sound and not in the least disturbing.

I did not give it a second thought until people started to bring this issue up in the boards.

I think it is a none-issue.

Probably the sound is just drowned out by the environment in most cases.

I also have the latest iMac 5K (late 2015) in quiet room and the fan at idle runs at 1200 rpm. It does make an annoying sound. I certainly can hear it. I have an SSD and no external spinning hard drive. I'm used to a very quiet environment. I had a mid 2011 iMac 27 before and I couldn't hear it when the fan was at idle.

When you run smcFanControl at full speed for a moment and lower it back to default, there is a moment where the fan runs below 1100 rpm before returning to the default speed and I can certainly attest that if we could have the idle set to 1100 rpm or 1000 rpm we would not hear this computer in a quiet room. The sad thing is, to my knowledge, that all the 5k CPU versions (3.2, 3.3 and 4.0) are all set to this default 1200 rpm at idle. So you would hear the same fan speed at idle whatever your CPU generates less or more heat. Our best luck would be that a firmware update is issued to lower it in the future, but I doubt it. Note there are no softwares that can lower the idle speed below the security level. I wish there were.

Yes, 1200 rpm is the default minimum fan speed on my iMac17,1, too, and it is normal that fan noise can be heard at this speed on this machine in a quiet environment. This does not mean that every mac fan can be heard at that speed, this depends on the hardware. For example, 1200 rpm on my MacBook Air7,1 make no sound at all. I have also read in a test that 27"-Macs tend to be louder than their 21" cousins.

I would like to note one thing: On my wife's older iMac14,2 (2013), the default fan speed is 1200 rpm, too, and it can be heard, too. On that machine, I somehow and miraculously managed to set the speed to 1000 rpm using a combination of fan control software (smcFanContol, FanControl and macs fan control) under Yosemite (still works under El Capitan). At 1000 rpm, that iMac runs next to silent. Alas, so such luck so far on my own brand new iMac17,1

Oh, just for the record: In the meantime, I have found out how to practically "silence" my iMac 5K Retina Late 2015 (iMac17,1) by lowering fan speed to 1000 rpm. If someone is interested, let me know.

I have an Air Cleaner and three drives connected so I've never actually heard the fan.

I would be hesitant to lower the speed anyway since it can't help but run warmer at 1000 rpm.

I am really pleased with all my Apple products, but disappointed that my (late 2015, 27 inch, Retina 5K, Fusion drive 2TB) iMac makes a whirring sound (only noticeable in a quiet room, but too loud). It runs at average fan speed of around 1200 rpm (between 33 and 35 degrees) and it is clearly audible. Is the 35 degrees normal (I use smcFanControl). Even when nothing is running (I mean apps etc) I can hear the fan noise clearly. My MacBook Air (late 2012) is silent in comparison and so is my late 2010 iMac.

Can I do something about this--other than get another replacement (this is a already a replacement, but the issue persist). how should i lower the fan speed to 1000 rpm and is this 'dangerous' because it will 'run warmer'?

Thanks.

I do not know for sure whether I can help you. I can only explain what I did and what worked for me. Try it out at your own risk, it is certainly not a standard procedure, let alone Apple-approved. No guarantees or liability on my part. And please forgive me for not describing the process in every detail, but only in rough sketches

I needed two programs, both downloadable from the Internet:

smc fan control 2.5.2

mac fan control (1.3.2).

I downloaded both and installed them, then quit them. Both programs are so designed that you can raise fan speed above factory settings, but not lower it beneath Apple's minimum setting - which varies from machine to machine.

The former program (SMC fan control) generates a respectively named section in the application support folder of the library (visible only when pressing "alt" in the "goto" menu.

There, I found a file named machines.plist.

This file contains the factory MSC fan settings for a lot of Macs, and also an auto-generated entry and the end named iMac17,1. I deleted the reference to auto-generation and edited (or, as you might say, manipulated) the values for min and sel speeds to 1000, and saved the file.

Afterwards, I went to the applications folder and right clicked the package smcFanControl and let the contents of the package show. In the resources folder of this package, I took the original machines.plist file and moved it to a safe place. then, I copied the edited version of the machine.plist file into this folder, so that it is now in both places.

I then opened SMC fan control and chose the command to reset to factory default. I restarted the Mac. After starting the program, I could see a new minimum value of 1000.

But this still did not change the actual RPM, the fan was still too noisy for my taste.

This is where the second program Mac fan control came into play. I opened it and chose the panel where you can set a fan speed by hand using a slider. Unlike before the measures described above, it was now possible to set the slider to 1000 RPM, which I did. Appearantly (and I do not know why and how), Mac fan control accesses the machine.plist of the competing smc fan control program.

Bingo! The fan slowed down to 1000 RPM.

I chose to auto start the Mac fan control software (not smc fan control). At every auto-start, the software will now set the fan to 1000 RPM. Sometimes, this does not happen after the Mac wakes up from sleep. In these cases, I just quit the program and restart it.

At 1000 RPM, the iMac can still be heard a little bit in a totally quiet environment, it is not completely silent like a MacBook air normally is. Nevertheless, it is almost silent, the difference is significant.

Naturally, the iMac runs a bit warmer at 1000 RPM. This is easy to monitor because Mac fan control rests in the menubar of OS X and can show you the CPU temperature sensor's reading as well as actual RPM.

At normal room temperature, my machine normally runs at between 38 and 48°C when the fan whirs at 1000 RPM, depending on cpu load, of course. I have not seen it exceeding that range so far. Also, no other sensor on the machine shows higher readings.

I have not done any testing as to the difference in temperature at 1200 RPM, but I think it may be between 5 and 10°C.

I am no expert, but I think I have read on the Internet that the CPU of my machine (i-6700K) can stand far higher temperatures (e.g. when overclocked).

Also, like I said before, I applied roughly the same procedure to my wife's iMac14,1 two years ago. It is still alive and kicking (and silent at that).

Besides, I have two Windows machines constantly running at temperatures in this range for years.

IMHO, Apple's engineers, like many of their colleagues at other manufacturers, were just a bit to conservative/protective when defining minimum fan speed on iMacs with dedicated GPU - but that is just my

Of course, I can not rule out the possibility that the lifespan of your CPU is shortened, and, like I said, I will not accept any liability for adverse effects if you try to do what I did. Enter at your own risk.

I did so myself. I just thought, chances are that I will replace my machine for other reasons well before its CPU dies on me for getting "too" warm constantly. And, in any case, I will have had the pleasure of near silence when using it (as opposed to not wanting to use it for the noise it generates).

Cheers, Marius...

I have a similar complaint about the fan noise as well. From calling Apple Care they had no record of any complaints on file regarding it which seemed surprising. For those who have returned the machines, has anyone had any luck in the replacements being any better?

At this point, I'm tempted to return mine for a full refund.

I have a 5K iMac with a 2TB Fusion drive, its silent, with the external time machine drive turned off I cannot hear the fan and I'm sitting right up close in a very quite room. I would get it checked out.