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iMac G5 fans misbehaviour

Message #1 - Posted 2006/02/17 - D.M. Procida

Of late - I don't how late - my iMac G5 has developed a nasty habit. AFter being turned on, the fans will very slowly increase their speed, first the System and Hard Drive fans, then the CPU fan. They appear to settle at a speed some several hundred RPM above the minima.

This appears to be independent of:

User
CPU usage
temperatures
/Library/Preferences

Hardware monitor shows the temperatures falling to their minimum levels, while the fan speeds continue to rise.

Also, the machine never wants to go to sleep any more.

Tomorrow I will try an archive-and-install to see if that helps. In the meantime, please send a postcard with suggestions to the usual place.

Daniele

Message #2 - Posted 2006/02/17 - Mike Jenkins

On 2006-02-17, D.M. Procida wrote:

Of late - I don't how late - my iMac G5 has developed a nasty habit. AFter being turned on, the fans will very slowly increase their speed, first the System and Hard Drive fans, then the CPU fan. They appear to settle at a speed some several hundred RPM above the minima.

If it's a rev. 1, take the back off and check for leaking/bulging capacitors.

Mike Jenkins
Dreamcast/Gamecube FAQs - http://www.kwik-e-mart.org Mike's Auctions: http://tinyurl.com/2374h X360 Gamertag: LilWashu360

Message #3 - Posted 2006/02/17 - Wayne Stuart

D.M. Procida wrote:

Of late - I don't how late - my iMac G5 has developed a nasty habit. AFter being turned on, the fans will very slowly increase their speed, first the System and Hard Drive fans, then the CPU fan. They appear to settle at a speed some several hundred RPM above the minima.

This appears to be independent of:

User
CPU usage
temperatures
/Library/Preferences

Hardware monitor shows the temperatures falling to their minimum levels, while the fan speeds continue to rise.

Also, the machine never wants to go to sleep any more.

Tomorrow I will try an archive-and-install to see if that helps. In the meantime, please send a postcard with suggestions to the usual place.

Daniele

Acquaintance of mine had a problem like this with his rev 1. Was the straw that broke the camel's back that led to this troublesome rev 1 being replaced with a shiny new rev 3 under guarantee.

This message was brought to you by Wayne Stuart - Have a nice day!

Message #4 - Posted 2006/02/18 - Tom Warner

D.M. Procida wrote:

Of late - I don't how late - my iMac G5 has developed a nasty habit. AFter being turned on, the fans will very slowly increase their speed, first the System and Hard Drive fans, then the CPU fan. They appear to settle at a speed some several hundred RPM above the minima.

Anything to do with this?

<http://docs.info.apple.com/article.html?artnum=303079>

Please let me know how get on with this problem.

All the best,
Tom

With or without religion,
you would have good people doing good things
and evil people doing evil things.
But for good people to do evil things, that takes religion.

Message #5 - Posted 2006/02/18 - D.M. Procida

Tom Warner wrote:

Of late - I don't how late - my iMac G5 has developed a nasty habit. AFter being turned on, the fans will very slowly increase their speed, first the System and Hard Drive fans, then the CPU fan. They appear to settle at a speed some several hundred RPM above the minima.

Anything to do with this?

<http://docs.info.apple.com/article.html?artnum=303079>

Not that, unfortunately.

It's a second-generation 20" G5.

The problem is very, very weird.

Normally, when the CPU's working hard, the CPU temperature rises rapidly and falls just as rapidly, as does the fan speed for the CPU.

Sometimes though, and I don't know what triggers it, the fans speeds will creep up slowly in a parabolic curve. Leave it alone long enough and they will descend again, but I don't know yet how far (that's how slow it is). The rate of ascent and descent, once this behaviour has been triggered, seems to have nothing obviously to do with temperatures, so far as I can see.

On the other hand, it survives a restart, but is gone after a long sleep.

Daniele

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