iMac Fan Speeds

[Big-TDI-Guy]

I have the humming sound going on my alu 20" imac, and seeing as it is constant when i rev up the fans using smcFanControl, it is impossible for it to be coming from the fans. I have instead ruled it out to being the HDD. It spins up nice and slow just like a drive does when i wake the computer from sleep.

If you listen carefully to your imac as it wakes from sleep, it will rev up the three fans individually, and then drop them down to lower speeds, meanwhile the harddrive will come to life and slowly rev up to its 7200rpm, and the humming comes in place.

Another weird thing I've noticed is that when I have my Maxtor OneTouchII drive mounted the noise starts to pulsate. This is probably because the drives run att similar speeds, 7200rpm, and there is interference between the two so that the noise is periodically cancelled out.

The hum from the external drive has the exact same frequency as the hum from the imac.

I think it's going in for repairs..

Yeah - it sounds exactly like hard-drive vibration. Unless it's really loud - I'm not sure I'd be too worried about it. I don't know if the Aluminum iMacs have elastomer hard drive mounts like the White iMacs. (I can't imagine Apple going backwards with technology - then again, I do have Leopard) But in all truth, some platters are balanced better than others, and will be quieter. If it is a lot louder than your fans - then I might get the mounting checked out (be sure it's in correctly) and maybe try and get another drive. I seem to be lucky in owning a very quiet iMac - so can't give you a huge idea - but I cannot hear my hard drive OR fans. The first thing I can hear in the dead of silence - is my backlight power supply FETs / Transformer (PWM) whining.

 

[vansouza]

why of why

Yeah - it sounds exactly like hard-drive vibration. Unless it's really loud - I'm not sure I'd be too worried about it. I don't know if the Aluminum iMacs have elastomer hard drive mounts like the White iMacs. (I can't imagine Apple going backwards with technology - then again, I do have Leopard) But in all truth, some platters are balanced better than others, and will be quieter. If it is a lot louder than your fans - then I might get the mounting checked out (be sure it's in correctly) and maybe try and get another drive. I seem to be lucky in owning a very quiet iMac - so can't give you a huge idea - but I cannot hear my hard drive OR fans. The first thing I can hear in the dead of silence - is my backlight power supply FETs / Transformer (PWM) whining.

Why slam Leopard as backward technology; if nothing else it is a true 64bit OS which is why for some of us it runs faster; which in my book is always better.

 

[airjuggernaut]

Yeah - it sounds exactly like hard-drive vibration. Unless it's really loud - I'm not sure I'd be too worried about it. I don't know if the Aluminum iMacs have elastomer hard drive mounts like the White iMacs. (I can't imagine Apple going backwards with technology - then again, I do have Leopard) But in all truth, some platters are balanced better than others, and will be quieter. If it is a lot louder than your fans - then I might get the mounting checked out (be sure it's in correctly) and maybe try and get another drive. I seem to be lucky in owning a very quiet iMac - so can't give you a huge idea - but I cannot hear my hard drive OR fans. The first thing I can hear in the dead of silence - is my backlight power supply FETs / Transformer (PWM) whining.

Thank you for that amazing Post

Im going to call apple care and send mine in for Repair.

 

[KurtangleTN]

Some great info in this thread, my iMac also seems to hum.

I originally thought it was a fan but it just seems to be so constant. I haven't brought it up for repairs yet, simply don't want to lug it an hour and a half for an annoyance, but sometime soon I will

How does Apple normally handle a potential hard-drive replacement, will they be able to transport everything from my current HD to my new one? I will of course backup some, but I'd rather not start from scratch.

Finally, has anyone replaced theirs for this issue? I have a bad feeling the Genius Bar will try to play it off as normal and my hour and a half trip is wasted, I'll have to have another hour and a half call to set this finally away.

 

[Big-TDI-Guy]

Some great info in this thread, my iMac also seems to hum.

I originally thought it was a fan but it just seems to be so constant. I haven't brought it up for repairs yet, simply don't want to lug it an hour and a half for an annoyance, but sometime soon I will

How does Apple normally handle a potential hard-drive replacement, will they be able to transport everything from my current HD to my new one? I will of course backup some, but I'd rather not start from scratch.

Finally, has anyone replaced theirs for this issue? I have a bad feeling the Genius Bar will try to play it off as normal and my hour and a half trip is wasted, I'll have to have another hour and a half call to set this finally away.

If it is your hard drive, an easy way to test for this is to "sleep" your iMac. While never having my iMac open when in sleep mode - most computers will power down the hard drive, but will remain "active". So the fans should continue to run, without the hard drive spinning. (you still need some cooling, in spite of the low-power state)

Another way to isolate is to run the Apple hardware test. At one point, this test revs the hell out of your fans - so if it is fan-vibration - this test will make it blatently obvious. (vibration tends to get a lot worse with increased revolutions)

My lazy cut-n-paste from Apple: (I believe this also works on my 2006 24" iMac)

Apple Hardware Test: iMac (Mid 2007)
Learn how to use Apple Hardware Test (AHT) with your iMac (Mid 2007) computer.

The iMac (Mid 2007) computer comes with Apple Hardware Test installed on a separate hard drive partition. This partition is not visible in the Finder.

To run Apple Hardware Test from the internal hard drive

Restart your computer while pressing and holding the 'D' key on your keyboard during startup.
Note: If Apple Hardware Test was removed by reformatting the drive, or if you cannot open it from your hard drive, you can still use Apple Hardware Test from the 'iMac OS X Install Disc 1' install DVD that came with your computer.

To run Apple Hardware Test from the Install DVD

 

[swek]

So a tech guy from the store where I bought and also brought my apple to for service called me today. He wrote it off as normal, since the other imacs in the store had the same hum. I guess, there's nothing I can do about it. He pretty much scared me off from having the computer opened since they would have to charge me about 1000 swedish crowns (like 130 USD) if there was nothing there to fix.

He is sending it back on monday, which in turn means I'm stuck with the same imac with the same hum. The only thing I guess would be to attempt to return it to the store, but that is just way WAY too much of a hassle, since i actually opened the box... sigh. Oh the swedish law...

So, my imac DOESN'T hum. It's NORMAL PEOPLE!

PS. He wouldn't even open the computer to check the drivemounts, I tried, but that would "probably cost me"..
damnit..

 

[ceres]

HI,

There has been occasional users with the new Alu iMacs having faulty temp sensers and hence fan going too quickly.

Your fan speed apear normal (the above ones run at 3500-4000).

Despite what the others say as the iMacs have three fans and thus are not silent , just are (very) quiet. It is normal for there to be an occasional soft noise tough this sould be just audiable.

That is correct. 0.2 Sone idle, 0.3 under heavy load for the 2.4ghz part and 0.5 for the 2.8ghz part. Very good values idle that would qualify for "ultra silent" in the build it yourself pc arena.