Problem with racing fans

gavspen · Post by **gavspen** » Fri Jul 04, 2008 8:32 am

The fans on my G5 dual 2.5 have always seemed to race at odd times, when the machine isnt doing much of anything. The logic board and processor have been replaced to no effect, but now something new. As soon as I press the start button the fans race at top speed and wont stop. I mean, it's alarming the noise they make, and it obviously doesnt have anything to do with overheating, since it starts immediately.

It happens 19 times out of 20, (this morning I cant get it to stop at all) and I can find no pattern. I've tried 3 different system disks (internal, external, CD), since when the hardware replacements didnt solve anything a software problem seemed a possible culprit , unplugged all peripherals including monitors (I still have cards inside though) and presumably the ram was checked when the other hardware was replaced.

It happens even when holding down "Option" on start up, in other words even before a start up disk has been chosen. Wouldnt that eliminate the possibility of a software problem, since it hasnt even looked at a system at that point?

I'm running 10.4.11, except from the CD which is a Tiger install disk, the cards still inside are a powercore and a UAD. I cant think of anything that's changed for quite some time, and the problem is brand new.

It sounds like a hair dryer.....I GOTTA TURN IT OFF!! Any ideas?

Gavin

bkshepard · Post by **bkshepard** » Fri Jul 04, 2008 8:59 am

Hey Gavin,

There's been a lot of talk about that over at MacFixit. You might do some nosing around there and see what you find. Good luck.

toofar · Post by **toofar** » Fri Jul 04, 2008 9:02 am

Hmm, I thought this was going to be a tirade about the freeways after a NASCAR event.

Sorry about your troubles, though. Wish I could help you.

gavspen · Post by **gavspen** » Fri Jul 04, 2008 10:21 am

toofar wrote:Hmm, I thought this was going to be a tirade about the freeways after a NASCAR event.

Sorry about your troubles, though. Wish I could help you.

I figured it wouldnt be long before someone chimed in with "I dont know what you mean, I was at the Belmont, and everyone was very well behaved", or words to that effect.

Now enough with the jokes, SOMEBODY HELP ME!! I'm going to turn on the vacuum cleaner just to mask the noise!!!

I'll check macfixit, thanks

Gavin

gavspen · Post by **gavspen** » Fri Jul 04, 2008 10:43 am

Macfixit wants me to buy a subscription to read the relevant articles, something I'm not inclined to do, but the little bit they do let you read says that some noticed a problem after installing 10.4.7. I'm using 10.4.11, and as I mentioned the problem starts immediately, before the thing even knows which system I'm going to boot to....I think, right?.... Idont really know what I'm talking about.

Gavin

cuttime · Post by **cuttime** » Fri Jul 04, 2008 11:20 am

Try re-setting NVRAM/PRAM. See the sticky in this forum.

robstudio · Post by **robstudio** » Fri Jul 04, 2008 11:26 am

It happens even when holding down "Option" on start up, in other words even before a start up disk has been chosen. Wouldnt that eliminate the possibility of a software problem, since it hasnt even looked at a system at that point?

Hey Gavin,
sounds like logical thinking to me... the other thing you could try is booting into target mode... press T when starting... That shouldn't load any software either... just to see... being you've tried the os cd and had the same result I'm thinking hardware related for sure... you haven't upgraded firmware recently??? Not even sure of the status of that on a G5, that's the only other thing I can think of... wait a minute... unless the firmware has become corrupted ... try resetting the pmu ..or pram whichever... sorry, SMU... oh hey check this out....

Restart while holding Option-Apple-P-R. You will hear the startup chime. Continue to hold the same 4 keys until you hear the chime 2 more times. and release keys to boot normally.
This process should bring your fans back under control.

from the link....
http://forums.macosxhints.com/archive/i ... 47992.html

See if that doesn't help...
Regards, Rob

Edited to add...
I believe I picked that up from Frodo! (Thanks!)... sorry for stream of thought post... took me a second to remember!!

PSS... I clicked on the link thinking... hey bud, what's your problem.. I'm a racing fan!!!

PSSS... what cuttime said

...

chucks · Post by **chucks** » Fri Jul 04, 2008 12:03 pm

Reset the SMU - instructions here:

http://support.apple.com/kb/HT1436?viewlocale=en_US

gavspen · Post by **gavspen** » Fri Jul 04, 2008 12:56 pm

Thanks fellas I'll try all that stuff tomorrow. Right now I'm off to consume half a cow and a bathtub full of booze.

Happy 4th

Gavin

gavspen · Post by **gavspen** » Sat Jul 05, 2008 11:10 am

Yipee!

Although it didnt "take" the first time, the second time I zapped the pram it seems to have done the trick. The fans are now behaving as usual, which is to say they only race sometimes, not ALL the time. I wish they would calm down in general but no one seems to know what to do about that.

I also did the SMU thing, just for laughs (which in my machine is labeled PMU, somewhat disconcertingly since somewhere in those links it says that Apple has retired that term), and so far through several restarts it's all holding up.

Thanks all. If it's get weird again I'll be sure to let you know

Gavin

MIDI Life Crisis · Post by **MIDI Life Crisis** » Sat Jul 05, 2008 11:58 am

gavspen wrote:Yipee!

Although it didnt "take" the first time, the second time I zapped the pram it seems to have done the trick.
Gavin

Why? Perhaps the PRAM reset your Energy Saver Preferences to have the processor run at AUTOMATIC instead of HIGHEST?

Sys Pref>Energy Saver>Options

If you leave the setting on highest, the processor will heat up and the fans are cooling it. If you leave it at automatic, it should keep the fans at a reasonable level.

gavspen · Post by **gavspen** » Sat Jul 05, 2008 2:53 pm

Just restarted and the problem came back. Zapped pram again, problem went away. I guess I can zap the pram every day for the rest of my life...sigh.

Any more thoughts?

By the way MLC, zapping the pram did not reset Energy Saver Preferences to highest, it stayed at automatic.

bkshepard · Post by **bkshepard** » Sat Jul 05, 2008 3:01 pm

If zapping PRAM each time fixes it, perhaps the battery is dead. Are you seeing things like the date and time not being correct, or other settings not "sticking" when you reboot?

gavspen · Post by **gavspen** » Sat Jul 05, 2008 3:13 pm

bkshepard wrote:If zapping PRAM each time fixes it, perhaps the battery is dead. Are you seeing things like the date and time not being correct, or other settings not "sticking" when you reboot?

Good thought, but no, everything else appears normal.

bkshepard · Post by **bkshepard** » Sat Jul 05, 2008 3:32 pm

Try this and see if it works.

1. Open the Energy Saver Preferences and set the processor to something other than "Automatic."
2. Close the Preference pane.
3. Reopen the Preference pane and set the processor back to Automatic.
4. Close the pane and reboot the computer.