G5 Pro fans running way too fast

Discussion in 'PowerPC Macs' started by fantoofast, Jul 28, 2009.

  1. fantoofast macrumors newbie

    Jul 28, 2009

    The fans on my G5 Pro are running at close to 3000rpm most of the time. I have read other forums and do not think this is normal at all.
    I started looking into the fans because I am getting frequent kernel panics (black screen crashes) and thought it might be the machine over heating.

    My CPUs are at about 50C to 52C and the fans are constantly running that fast.

    Does anyone have any idea why this might be and what I can do about it?


    Attached Files:

  2. wpc33 macrumors 6502


    Jul 2, 2006
    Vancouver, BC
    Two possible fixes:
    Reset the SMU with these instructions

    Go in to Open firmware and reset PRAM.

    Press and hold the Command-Option-P-R keys

    To access Open Firmware press and hold Command-Option -O-F

    At the Open Firmware prompt, type: reset-nvram

    Press Return.

    At the Open Firmware prompt, type: reset-all

    Press Return.
  3. Loa macrumors 68000


    May 5, 2003

    Are those fans revving up as soon as you start-up?

    Also, I've had the fan maxing-out problem in May with my iMac. Ended up replacing just about everything inside it. So if you're getting kernel panics as well, make regular back-ups as your machine could crack at any time.

  4. geoffreak macrumors 68020


    Feb 8, 2008
    I don't know if those temperatures are normal for a PPC machine, but the Intels can handle up to 80 degrees C before overheating problems start to occur.
  5. gugucom macrumors 68020


    May 21, 2009
    Munich, Germany
    G5 fans need to be calibrated after hardware changes to the CPUs. So there is a chance you made a change or your system falsely got the message that something changed. I believe an intermittant CPU failure could cause such a secondary problem. G5 PMs are known to have intermittant CPU failure before a CPU fails completely.
  6. jpmeyer macrumors newbie

    Jul 28, 2009
    Chicago subrubs
    RE> G5 fans too fast


    It appears that you have the Quad G5, as do I. I second the suggestion to reset PRAM and SMC, although those fixes ultimately stopped working for me. I am just finishing a DIY re-build of the liquid cooling system on my G5. No leaking, but one of the CPU cooling blocks had become blocked. Thus, the pumps were working very hard to push enough coolant to keep the temps down. One of my CPUs was regularly in the 70 C range under load, the other was much cooler, and I also experienced frequent freezes.

    Although I have had fun with the rebuild project, I wish that I had tried harder to get Apple to fix the problem. Many G5 users have reported here and elsewhere that Apple has repaired or replaced leaking G5s many months after the expiration of warranty/AppleCare. If the resets don't work for you, I suggest polite but firm interactions with Apple.

    Good luck!

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