Question about Apple PowerMac G5 Dual Mac Desktop

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PowerMac G5 fan keeps running -- LOUDLY

I have a three-year-old PowerMac G5 desktop, the last of the pre-Intel dual-core models. I'm pretty sure you don't need all the specs to answer my question, because the problem is with the fan. Three days ago, it came on and since then, so long as the machine is awake, it never shuts off. It has GOT to be about 120db, ridiculously loud. It used to only come on when the machine locked up, in conjunction with the red light of death lighting up on the front of the tower. But now it has come on with the machine still running and never shuts off. It is like sitting in the room with a jet engine. I suspect this either means my CPU is running hot, or else my thermostat has gone buggy and just THINKS it's running hot.

Suggestions on how to shut it off without disconnecting it?

Posted by hagakure on


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I had the same problem... It is the logic board... You need to get it replaced. One way you could try to fix it by resetting the board there should be a little black dot behind the front two fans when you open it up. Press and hold for a few seconds... this resets the board to factory settings. The other way is replace the internal battery. and the third is to replace the logic board. $150-200

Posted on Jun 21, 2009



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I was having the same FANS RUN RIOT problem but only when I left the OSx LEOPARD install disk in it...with the install disk in..It would somehow wake FROM SLEEP to a 757 aircraft engine roar

Posted on May 25, 2012


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The red light in question will come on and the media bay fan will spin at high speed if the plastic air deflector door is not in place, OR the white sensor label on the lower right tab of the air deflector door is damaged or out of position, OR the air deflector sensor board is faulty.
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