PowerMac G5 top exhaust fan now full speed...help!

Discussion in 'PowerPC Macs' started by tom vilsack, Mar 29, 2014.

  1. tom vilsack macrumors 68000

    tom vilsack

    Nov 20, 2010
    ladner cdn
    So last night I decided to give my PowerMacs 1.8dp (pci ver) rear exhaust fan a good cleaning...unplugged it and took it out cleaned,replaced....Now the top exhaust fan is on full power (sounds like a jet ready for takeoff...errrrrr) all the other fans including bottom exhaust fan running as per normal.

    What do I do?

    -Ive tried all the normal routines,reset PMU,Pram ect...nothing!

    I've read about needing some apple "Thermal calibration dvd"???

    If so,what # and where do I get it?
  2. Intell macrumors P6


    Jan 24, 2010
    Did you remove the CPUs? Exactly which fan is this? Did you try plugging in the previously disconnected drive bay fan?
  3. Altemose macrumors G3


    Mar 26, 2013
    Elkton, Maryland
    You are going to need to purchase an Apple Service Diagnostics 2.5.8 disk in order to recalibrate the system. However, I do not see why this is necessary as you did not remove the CPUs.
  4. DeltaMac macrumors G3


    Jul 30, 2003
    If you actually did remove the CPUs as part of your cleaning, and swapped the positions (upper to lower and vice versa), then the calibration would, in fact, be necessary.
  5. jbarley macrumors 68040


    Jul 1, 2006
    Vancouver Island
    You need ASD 2.5.8 and should be able to get it here,
    If by chance this does not work, PM me and I'll make an image of my copy available for you.
  6. tom vilsack thread starter macrumors 68000

    tom vilsack

    Nov 20, 2010
    ladner cdn
    -no I did not remove cpu's
    -fan I removed was rear exhaust fan/s
    -yes re plugged in drivebay fan

    -downloaded and ran both complete test and thermal cal...all came back fine

    *** On test cd I notice there was no test setting for Rear Fan A "Exhaust Test" (which is the fan running full blast) There is a test for Rear fan B "Exhaust Test"***

    For whatever reason even the test cd can't detect? rear fan A exhaust...

    Any more ideas?
  7. ahender macrumors newbie

    Apr 11, 2014
    Racing Fans Solved...

    My husband has a G5 dual core 1047 model. Recently while in use it froze - reasons unknown - may have been power related but at this point it doesn't matter...

    When the machine was restarted the fans came on full blast and would not stop.

    I tore it down - CPUs w/heatsinks as a unit came off too, removed and cleaned out power supply too. this machine was incredibly dirty (he has been properly admonished) re-assembled reset the pmu and pram and replaced the never-before-replaced on board battery. Fired her up and life was GREAT!! but then it happened... firmware was 1 rev behind... updated the firmware and POOOOOOF fans like crazy again... bummer.

    Then one of the CPUs gave out... ordered 2 more... and installed them both retaining the known-to-be-working CPU as a future backup... and I surmised that must have been why the fans were going nuts... a dying CPU..

    Of course you all know that if you replace CPU(s) you have to calibrate the fans using ASD except that it won't let you due to weird errors... unless you try this trick!!!(for my machine it is 2.5.8, different models need different versions so get that straight before you do this)

    I can't say that it will work for everyone, but it worked like a freaking charm for me. After trying to calibrate the new CPUs together with no luck, I started trying combinations. First I should tell you that I was getting any number of errors running the diagnostics... all of which I took to be errant as they were a)telling me the CPUs had eeprom errors, then I got IC2 errors, (sometimes the machine would boot to the OS with half the GHZ it was supposed to have btw), got fan errors, you name it, I got it as an error when trying to calibrate the fans...

    Then I realized that I hadn't really followed the directions found in the readme for ASD 2.5.8 which states that you should:

    FIRST: insert disc, hold down "c" while booting until you see the ASD "loading" screen. This boots diagnostics in OF mode which doesn't use the OS. Run all tests.
    SECOND: SHUTDOWN (NOT RESTART) the machine and reboot holding down the option key which boots the diagnostics in OS mode... right arrow until you see the option to boot OS diagnostics, click it, click the arrow key, wait a while for OS diags to come up (it may take a while so DON'T get impatient)

    THIRD: Choose only the CPU and Memory tests and run. (you should get a PASS - otherwise I can't say if this will work for you or not)

    FOURTH: SHUTDOWN the machine and start holding down the "c" key again to boot into the OF diagnostics (you don't have to choose it, it boots to this automatically)

    FIFTH: Go IMMEDIATELY to calibrate fans - you may get failures a few times DO NOT let this discourage you... One or both of the CPUs should calibrate - even if you get a failure on one CPU to calibrate but get success on another CPU DO NOT rerun calibration...

    after calibration on at least one CPU shutdown and restart normally.

    If the fans slow down but still run fast - do the ENTIRE procedure again.

    Amazingly, after working on this <expletive> machine for 10 days and about 30 hours of intensive geekitude doing it...

    My machine now boots and runs SILENTLY :D

    If you are still having trouble - take out one CPU, run the above steps and then re-install the second CPU and do the steps again..

    (ultimately the combo that worked for me was Good CPU ALONE in the first position on the board (if you have it in the wrong position the machine won't boot so there's the big clue for you which spot is the first one...) calibrate using OF Diags, install second CPU, follow steps above which then issues error on first CPU but calibrates the second one.. go figure...)

    Tedious, yes definitely... Possible Cure? most assuredly.

    My thinking is that the OS diags reset some errors somewhere...or zeros them out which then allows you somewhat successfully start down the path of calibration.

    Hope this helps...

    ASD 2.5.8 can be had for those willing to do a torrent of searching...

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