Power Supply Fan constantly Running at 2800rpm's

[TwistyO]

OK, here's the situation. I moved to a new office and a new computer after someone left. It's a late 2006 Mac Pro running 10.4.11 with Nvidia Quadro FX 4500. The Power supply fan is always running at 2800rpm from startup.
I've reset the SMC and PRAM
Plug directly into wall
tried Using SMCFanControl
Dusted it out (there was none)
All temps are normal (amb -72, PowerSup 1&2 77&72)
Tried another fan, still goes at high speed

Hardware test gave me this error code - 4M0T/1/40000003S

I'm stumped. I guess what I need to know is what that error code means and/or what controls that fan speed, ambient board or a board in the power supply itself?

Any help would be appreciated, I've been working with the sound of a low flying aircraft for weeks now.

 

[djackmac]

Either the logic board is triggering the fans to ramp up or the power supply itself. Have you booted to something else like the install dvd or preferably a clean OS to see if it is doing the same? Where did you happen to get another power supply fan?

 

[TwistyO]

Yes, I have done a clean install too. I plugged in the exhaust fan to see if I got the same result.

 

[djackmac]

Considering there is nothing else close to the power supply that is setting the fan off, I'd say there is a good possibility that could be the cause. I've seen faulty power supplies cause fan issues on a few occasions. For example not too long ago had an aluminum iMac with a HD fan running at higher RPMs than normal and it turned out to be the power supply.