G5 fans run full speed all the time, what to do?

Discussion in 'PowerPC Macs' started by btc, Sep 3, 2010.

  1. btc
    macrumors member

    Jan 29, 2006
    My step-son works for a company that uses a variety of computers in their test dept. and when they upgraded the test equipment they gave the old stuff to employees.

    My step-son is a dyed-in-the-wool PC guy who doesn't care for Macs so when he saw a G5 PPC sitting there he took it home and gave it to me.

    It's a 2.0 GHz dual-processor with 8x AGP video. I checked it out and the only thing "wrong" with it is that someone has set up the fans, all of them, to run full-speed all the time.

    First, how did they most likely do that and, second, how can I return the fans to their normal operation. This can't be good for the computer and it's so loud and annoying that I'd rather use my G4.

    It's a great computer otherwise, I hope they didn't do something permanent that would require a new motherboard, that's not in my budget.

    Help me out here.

  2. macrumors 6502

    Mar 16, 2007
    First, If the red light is on, ensure that the plastic air deflector is installed properly.

    Press the reset button on the motherboard
    Boot the machine and press Command + Option + P + r
    -if that doesn't work-
    Hold the power button down until you hear a long beep.
    -if that doesn't work-
    You'll need to calibrate the fans in Apple Service Diagnostic.
    -if that doesn't work-
    Your temperature sensor is busted, unplug the drive bay temperature sensor and reboot. Other than that, I think the only fix is a new motherboard.
  3. macrumors 6502

    Sep 27, 2007
    Philly, PA
    There is no way to set the speed of the fans on a G5. Check to see if there is a red light on on the motherboard itself is on like the poster above me said. There is a plastic, clear air deflector installed when you open the case, correct?
  4. macrumors 6502

    Jan 14, 2002
    Los Angeles and NorCal
    try putting sleep to "never". Then restart the computer.
  5. macrumors 6502a


    Sep 11, 2006
    Great Britain (Glasgow)
    You could get a temp monitor app and see if any of the sensors are reading something unusual :confused:
  6. macrumors 68000


    Oct 29, 2005
    Portland, OR
    Even if the deflector is in place you may still have it to blame. Take the deflector out (the gigantic piece of clear plastic inside the case) and look at the lower right-hand tab (on the bottom, slots into place). There SHOULD be a sticker there; this is what blocks the sensor and tells the machine that the case is assembled. If this sticker is missing, cover the tab on the machine facing site with some duct tape. Problem (possibly) solved. :)
  7. macrumors newbie

    Oct 22, 2014
    plastic cover fixed fans

    impossible to believe this worked but many many thanks to disconap for the tip on the little "tape" on the bottom right tab of the plastic deflector. Somehow i had a cover that was missing this tape and putting a piece of duct tape there made the fans stop. Sometimes it is the little tings in life that matter.
  8. macrumors G3


    Mar 26, 2013
    Elkton, Maryland

    Either the plastic air deflector is not being detected as stated above or someone removed the CPUs for repairs or other reasons and forgot to recalibrate the fans in Apple Service Diagnostics.
  9. macrumors 6502a


    Sep 11, 2006
    Great Britain (Glasgow)
    Great to hear its finally fixed
  10. macrumors 6502

    May 27, 2013
    Is there anything duct tape can't do?
  11. macrumors 68020


    Aug 22, 2014
    tape air ducts well

    (seriously, duct tape is the worst thing for sealing air ducts, ironically)
  12. macrumors regular

    Jun 28, 2007
    My G5's fan use to blare so loud I thought it was going to blow up. I was told to blow out the dust (carefully), and it worked. Apparently, the area that keeps track of raising and lowering the fans, were covered with dust. I think I posted this problem on this forum.


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