Mac Pro 5,1 psu fan speed

[mereditp99]

I've just acquired a 2010 4 core 3.2 mac pro, running Lion and with the optional 5870

The psu fan seems quite noisy and running smc fan control I can see it's running at 1500rpm with no load on the system

Reading around other people are getting 600rpm at idle, but looking at smc settings my *minimum* speed is 1500. I can increase it, but not take it any lower

The Pro was very dusty inside when I got it and I've cleaned out everything I can see with an air can, but not the psu as that seemed a slightly bigger job taking things apart.

Is it possible a dusty/clogged psu will make the fan spin faster?

All fan speeds:

pci 1500rpm
ps 1500rpm
exhaust 600rpm
intake 600rpm
boosta 856rpm

Temps running 24-28C.

Thanks, Pete

 

[mereditp99]

update - tried a PRAM and SMC reset, made no difference

 

[derbothaus]

Is it possible a dusty/clogged psu will make the fan spin faster?

Yes. Very possible.

 

[BigJohno]

Take the CD drive tray out and you can get access to the fan. Then just blow a ton of air through there.

 

[mereditp99]

Well, that made absolutely no difference.

Does anyone which temperature sensor drives the psu fan, and where it is?

Might try installing Snow Leopard and see if that makes a difference

 

[mereditp99]

yep, psu fan down to 675 rpm after a clean SL install.

very strange. time to start installing/patching things one step at a time I guess.