Mac Pro rear fan runs at high RPM

This actually sounds like duplicate of someone else's thread very recent from last 10 days or less. that program is to increase fan speed to improve air flow with higher rpm over the default.

Thermal sensor reading details? that would provide practical details - install the most accurate: Hardware Monitor and report what it shows.

dust, faulty connector of one of the thermal sensors. Be paranoid and assume nothing works and troubleshoot lookng for anything really.

In the meantime with overly hot weather buy some dry ice or liquid nitrogen to cool down; for all I know the thermal paste went bad; or you are using unapproved FBDIMMs that don't have heat sinks.... endless possibilities! <g>

Open it up and get to know the insides and play around with this little dust devil power vac for computers and electronics

http://www.amazon.com/Metro-Vacuum-ED500-500-Watt-Electric/dp/B001J4ZOAW/

Improper or poorly seated power cord / using a UPS (good idea) but not 850W+ (bad)

I just downloaded two apps for controlling fan speed on my MacPro 2.93 Mhz. Not sure if I even need the apps, but I thought I'd give them a try ....

I installed Fan Control which only allows me to control the Left (PCI) and Right Fan (PS). I have no idea what PCI and PS means ...

smcFanControl allows me to control all five fans, with a Menu Pull Down Read-out showing speeds of all five fans.

I think this could really come in handy during the hot weather. My bedroom gets up to 100 Degrees F. (37.7 Degrees C.). I've seen computer temperatures over 170 Degrees F. (76.6 Degrees C.) in the summer.

Are there any other Fan Control Apps that would work on my MacPro 2.93 Mhz?