PM G5 Quick fan related question

[Mattww]

Has anyone else seen and resolved a similar issue to this?

On my G5 2.5GHz Dual with X800XT when idle iStat Pro reports fans speeds:

CPU B Exhaust 300rpm
CPU B Pump 1250rpm
CPU A Intake 300rpm
CPU A Exhaust 300rpm
CPU B Intake 300rpm
CPU A Pump 1250 rpm
Drive Bay 1000rpm
Slots 122rpm
Backside 51rpm

Despite this after about 5 minutes of use either after waking from sleep or a restart there is a fan that get louder and it is a really grating pitch that gives me headaches if I don't put on some music a DVD or something to drown it out. If I put the Mac to sleep it goes away again but only for a few minutes.

If I give the machine heavy tasks like video encoding the cpu fans etc speed up as expected and with a demanding game I can hear the video card fan but this constant noise is different to both these situations.

I have tried shutting down and up plugging the mains, messing with energy saver processor settings and before I had a problem with my upper drive bay (now getting IOATA controller blocking bus errors if I attach any drive in this bay) the problem still happened when booted from either hard disk, one with 10.4.11 and the other with 10.5.2. I have also blasted the dust out of the case with compressed air and the problem persists.

 

[Mattww]

I guess no one else has seen this then?

I found the PMU reset process and press the button on my G5. It reset the date and time so I know the rest worked but I am still seeing the same issue. I get 5 minutes of quiet (not Mac Pro levels but not too bad) then the noise picks up and stays that the louder level with the normal revving when doing intensive tasks.

Also no change deleting the powermangement prefs form /library/preferences

 

[Quint]

Have you ever had the logic board replaced on your Mac?

 

[Mattww]

Have you ever had the logic board replaced on your Mac?

No the board and processors are original. The changes I have made are extra RAM (added at time of purchase), hard disks (upgraded replacing original), optical drive (swopped for Pioneer 109) and X800XT card (replaced OEM 9600XT). None of these changes seemed to trigger the issue. I am beginning to suspect a sensor problem as the iStat fan values seem to be similar to those posted elsewhere and temperatures seem normal.