Fan noise. speed...and how I solved it.

Discussion in 'iMac' started by Halcyon, May 17, 2008.

  1. Halcyon macrumors 6502

    Sep 21, 2006
    A while back I posted about a rather strange and bothersome "clicking"noise with my 24" iMac. I coul not positively identify 100% where the noise was comming from or what was originating it. All I knew was that when I put the computer to sleep the noise would go away.

    If I had to describe this clicking noise the best would be something like " seems that the blades of one of the fans would be lightly touching a wire or thin cable, as they spin...". This narrowed it down to one of the moving/spinning components, but which one was the question.

    Therefore I installed a nifty little application called smcfancontrol and decided to play with the speed of the different fans. To make the story short, I narrowed it down to the fan of the hard drive. How/Why? Because when I increased the minimum fan speed for this one fan the noise went away. This fan normally runs at about 1200 to 1300 rpm (at least in my machine) and at those speeds it kept the operating temps with normal range. Never before have I had an overheating problem, nor do I have it now.

    I have this particular fan set to a minimum speed of 1967 rpm, which is the minimum for the clicking noise to disappear. What was going on? I don't know for sure, but maybe a wire was to close to the fan blades and now that the air flow is greater due to the increased speed, the air itself is blowing the fan away and keeping it at a safe distance. I don't know if this fans sit on a bearing, but another possibility might be that that higher speed makes for a smoother ride due to the generated momentum. This is all speculation so please those of you that are familiar with the guts of these machines, jump in and correct me if necessary.

    Bottom line is that I got rid of the annoying clicking noise, but being that it was done in a rather unorthodox manner I hope I am not generating a bigger problem down the line. Am I shortening the fan's life by making it run at a continuos higher speed than normal? Maybe I'm just masking the problem and an impeding catastrophic failure from another component is awaiting down the road?

    For analysis purposes, the machine is working just fine in every other aspect.

    Anybody care to jump in with any ideas or suggestions...I'm sure this will help others that had the same problem.
  2. JNB macrumors 604


    Oct 7, 2004
    In a Hell predominately of my own making
    A lot of us use smc, and have no problems. I keep my MacBook higher than that without issue.

    If you're iMac is still under warranty, I'd get it to Apple to investigate. If there is a wire or other piece being brushed by the fan, that ain't right. It should be looked into and repaired. While the fan may not be a problem, a wire being slowly sliced surely will be.

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