1600SC rear fan too fast

[Erwin Abbott]

Hi,

I've noticed the rear fan in my 1600SC seems to be running much faster
than usual, though I don't have logs to know what the baseline is.
Here's the sensor output (using OpenManage Linux kernel plugin)

Front FAN RPM = 1721 RPM
Rear FAN RPM  = 3375 RPM

CPU 1 FAN RPM = 3125 RPM
CPU 2 FAN RPM = 3183 RPM

CPU 1 Temp    = 87.8 F
CPU 2 Temp    = 84.2 F

Planar Temp   = 82.4 F

The server is rarely under any load and the planar temp has kept
pretty constant... so it seems to be running abnormally fast.  I
recently shut the server down and cleared the little bit of dust that
has collected, but no change in fan speed.  The server has a single
power supply and the case is fully closed.

First, is the fan actually running fast... should I worry about it
failing?  Second, what can I do to troubleshoot?

Thanks,
  Erwin