PowerBook G4 fan whine, system freeze

F

fhuddles

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My PowerBook (G4 Aluminum 1.67 Hi-Res) has made a low "grinding" noise in the upper left when the cpu is under load for a time: this seems to be the left rear fan. Some time ago, though, it suddenly started making a high whine, after some time of activity. Sleeping the computer or decreased cpu (and fan) activity would stop the noise, and it would take a while to start again. In other words, it seemed that the fan would run for a while before going into this whining mode. But at one point, the system just froze up. I had to reinstall Mac OS X to get it useable again, but otherwise nothing was lost on the disk: all my data were in "Previous Systems".
Now I'm checking fan activity using the iStat dashboard widget, and I see the left fan runs sometimes as high as 2400 rpm, while I have never seen the right fan at anything other than 0.
Also, I was able to check the fan activity while this "whining" noise was going on: the fan speed went down dramatically, to 300 rpm or less. Cpu and Power Supply temperatures started rising.
So: could the rise in temperatures as a result of fan malfunction have caused the system freeze-up?
It seems obvious that my left rear fan is bad and needs to be replaced. But what's going on with the right rear fan? Is that normal, to stay inert while the left fan whirs away?

Thanks...
 
Yes, yes, and yes. I think you already diagnosed the problem exactly.

Fans are detrimental to the proper operation of any computer -- excess heat build-up can cause any number of odd behavior symptoms, and can even cause permanent damage to the computer. I would highly recommend not turning the computer on at all until the fan problem is fixed, as if something were to go horribly wrong and melt and/or fry because of the lack of a working fan, then the repairs to the computer may rise to a level that's simply infeasible to justify, not to mention making the computer useless and broken.
 
I've got the machine sleeping peacefully. But I want to make sure I understand: you are saying it's normal for the right fan to be at 0 when the left fan is active? This might be normal: maybe the right fan handles a different part of the computer which doesn't need the cooling at that point. I just want to make sure that part of my problem isn't that the right fan is not coming on when it should, thus forcing the left fan to work harder than it should.
By the way, before I restored the system I ran the Apple Hardware Test, which I am told tests the fans, and everything passed. I did not run it continually, though: I can see how it would miss this left fan problem, because the fan runs OK for a while: a little loud, but OK. And I assume the test tested the right fan and it passed.
So: the right fan at 0 sounds normal?
Thanks.
 
I would think that the fan would run continuously, just at a very low RPM -- it does NOT sound normal to me that the fan is turning 0 rpms, though.

I don't know enough about the PowerBook G4 to say whether or not that's normal -- all I can say is that for computers in general, fans are essential, and broken or improperly functioning fans lead to system meltdowns and physical damage to the electronics inside.
 
Call url=http://www.macservice.com/]MacService[/url] and see if they can fix that problem. Your other choice would be to find you local Apple Specialist and see if one them can help.
 
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