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What is a typical Hard Drive fan speed when the temp is around 100 on a 24 inch iMac 9,1?

I have three iMacs;1) Mid 2007 20 inch (7,1), 2) Early 2009 24 inch (9,1), and a late 2009 27 inch (10,1). The 20 & 27 inch models have a hard drive fan speed of around 1200 RPM when the temp is in and around 100 degrees. My 24 inch is around 1600 RPM. I purchased the 24 inch used, and the original owener had to take it in for repair due to a high fan speed right before I took posession. Apple replaced the logic board, LCD, Fan, and I think a fan controller. When I got it, I thought the fan sounded just a little loud. I have not been able to determine if 1600 RPM is normal for this model becuase it was set higher by Apple, OR if something else is wrong. I have not found any posts or anyone knowledgeable. I have found more information about users wanting to speed up the fan. Note, I have tried an SMC and PRAM reset. The are all running Lion 10.7.2.Note that the hard drive temp sensor appears to be working. For example, if the machine has been off for a few hours, the HD temp is near room temp. If on for a while, the HD temp runs around 100 degrees. No hard drive swaps that i know of. It came straight from the Apple Store repair to me.

iMac, Mac OS X (10.7.2), model identifier 9,1

Posted on Oct 28, 2011 8:12 PM

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10 replies

Oct 29, 2011 6:10 AM in response to Tom Fish

100F or almost 38C for the drive is running quite cool and the speed at that temp shouldn't be above idle. I don't know exactly how fast the HDD fan should idle for your model, but it should be close to 1,000 or below. 1,600 at that temp is running fast.


I've heard that several SMC resets are sometimes necessary. You should try the Hardware Test in extended. An error may not turn up until several runs through.


http://support.apple.com/kb/ht1509


Even if the AHT doesn't turn up an error, something's wrong. You might be able to bring it back for repair under the original owner's warranty, usually three months.

Oct 29, 2011 8:39 AM in response to virg

That is interesting. I was extrapolating from my 21.5 with a default idle HD fan speed of 1,100. I've always seen the bigger models running slower speeds at idle; the fans are bigger with larger fan blades and the lower speeds presumably can provide equivalent air flow and cooling. Just now searching, I came across one other 24" running a HD fan at 1,600.


So don't know what to say is normal for the 24" The only thing is I'm surprised the fan can be heard. Apple has a reputation for silent running fans, at least at low temps, and that the fan can be heard leads me to believe that this may not be right.

Oct 30, 2011 5:51 AM in response to WZZZ

I have tried PRAM and SMC resets a few times. I am running Lion, and I can not get the AHT to work. I have read many posts & threads about this topic too. I wish Apple would just have a download site for the AHT and some basic diagnostic tools. I haven't seen anything yet that convinces me that 1600 is not too fast. I don't think it is excessive, but I still think there may be a firmware setting or something that is not exactly correct. Supposedly a tech from an authorized Apple Service center is going to call me on Monday. I would hope there is a specification, or at least a procedure to go through for calibrating the temp sensors when either the logic board or a sensor is replaced.

Nov 9, 2011 3:55 PM in response to Tom Fish

As a follow up, I spoke with Apple Care via phone. And after consulting with a senior advisor, the Apple Care person thought I should set up an appointment at the Genius Bar. One of the two Genius Bar persons at the store thought that 1600 was OK. The other Genius Bar person offered to replace the fan (and sensor if the 9,1 has a sensor). We both agreed to just watch it for now. So, the HD fan runs about 1600 RPM, slightly audible unlike my other two iMacs. As an FYI, all three fans were replaced in the recent repair under the Apple Care Agreement. It would be interesting for me to understand how the fan speeds are controlled and measured. In some larger applications that I am familiar with, sometimes motors are unpowered for very brief periods of time, and the back emf is measured as an indicator of speed. (Vehicle Anti-Lock Brake Motors). In all the people I have spoken with at Apple, no one could find a spec on what is normal. I thought that was odd, and I'm really not satisfied with that response.

What is a typical Hard Drive fan speed when the temp is around 100 on a 24 inch iMac 9,1?

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