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Problems with G5 fans coming on...

577 Views 7 Replies Latest reply: Jan 26, 2013 4:08 AM by tekno.mac RSS
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Jan 10, 2013 2:15 PM

I have a very early Power Mac Dual 2GHz PowerPC G5 running OSX 10.4.11 which has started having strange problems... For apparantly no reason all the fans come on and stay on - this can sometimes be resolved with a restart, sometimes not, in which case I need to shut the machine down - after which it will sometimes not reboot the first time (gets as far a blue screen then hangs) - I then need to unplug it from the mains for 10 mins or so, afer which it will start up normally.


Looking into the problem I have discovered this message in the system log every time it happens:


Jan 10 22:01:19 teknomage kernel[0]: AppleMaxim6690::readI2C error (0xE00002C2) I2CAddr = 0x98, subAddr = 0x01

Jan 10 22:01:19 teknomage kernel[0]: AppleMaxim6690::getExternalTemp read temp failed!


I have also started running a temperature & hardware monitor to try and get to the bottom of this and have discovered that all my temperatures show a flatline when the fault is about to occur. If I then restart the machine, all fans will be running. If the machine starts up with all fans running. On one occasion, CPU A showed a flatline temperature of -6.1 degrees  for several hours (with the machine working just fine!) and the machine restarted into all fans running mode after this.


I have tried both replacing the battery and resetting the PMU - which appeared to fix the fault for a few days, it then recurred.


The machine also will not sleep properly - in that it won't always wake from sleep and needs a power off and reboot - which sometimes occurs with all fans running.


Apart from that the machine works fine - all my software works etc even when all fans are running.


Any ideas as to the cause? I've not changed the hardware (except to replace the battrery when the fault first started) or software for over a year. Is it case of a failing logic board or could it be something else? Any ideas on how to resolve this?


Is there any problem in running the machine when the temperature monitor is showing flatline temperatures for all sensors - or is there a lower level system that will protect the machine should temperatures get too high (maybe by switching to all fans running?)

PowerMac, Mac OS X (10.4.11), Dual 2GHz PowerPC G5


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