Is it possible to overspin an iMac G4 fan?

Discussion in 'PowerPC Macs' started by CooperBox, Jun 13, 2016.

  1. CooperBox macrumors 6502a

    CooperBox

    Joined:
    Nov 28, 2010
    Location:
    France - between Ricard & Absinthe
    #1
    Reading back through some older threads on G4 iMac's, I came across this comment, "While you have the unit totally open and drive bay removed, vacuum/blow out the years of accumulated dust. Use a pencil to hold the fan stationary so the air blower doesn't over-spin it."

    Several times with hard drive & optical drive removed, I have cleaned the internals of disgustingly dirty iMacs with a high pressure air supply (not a pressurized can), and recall that the fan inside at the top has spun remarkably quickly. I'd then remove any residual dust from individual fan blades using a soft brush.
    My question is simple. Could these (and similar fans) overspin, with a subsequent drop-off of efficiency? And what adverse affect (if any) if a fan ran 'backwards' during hi press cleaning - as I'm sure all mine must have at one time or another.
    All four of my G4 iMacs have been thoroughly cleaned internally with high pressure supply, and all seem to function ok. However the fan of one 20" runs fast (is notably more audible) immediately following boot, and is the same during functioning. The other is barely audible.
    I'd be interested to hear comments and experiences of others.
     
  2. jbarley macrumors 68030

    jbarley

    Joined:
    Jul 1, 2006
    Location:
    Vancouver Island
    #2
    Like yourself, I've cleaned many a computer fan, power supply, etc. over the years using air from my shop compressor, and to date I've never noticed any problems whatsoever.
     
  3. CooperBox thread starter macrumors 6502a

    CooperBox

    Joined:
    Nov 28, 2010
    Location:
    France - between Ricard & Absinthe
    #3
    Thanks for the comments, which are somewhat reassuring.
     
  4. Johnny365 macrumors regular

    Johnny365

    Joined:
    Nov 30, 2015
    #4
    I reckon if the fan spun the wrong way or too fast, that it could damage the motor?
     
  5. weckart macrumors 68040

    Joined:
    Nov 7, 2004
    #5
    Small brushless fans are a bit more delicate and the pressurised gust from these cans can damage them so that they do not spin straight. It is a judgement call as to how delicate a particular fan is. Nevertheless, there is no point letting the blades spin if you are trying to blast gunk off them so always hold the blade
     

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