CPU fan can't go faster than 3000 rpm?

[Opticreep]

When I first built my Athlon 64 (NForce3-based) system, the system ran
pretty hot. Idle at 45 degrees, and it would often go as high as 60
or 65 degrees. The CPU fan usually started at 3000 rpms when I start
up the computer, then worked its way up to 4500 rpms after a few
minutes (and stayed there).

I fiddled around with the system, installing better drivers,
rearranging case fans, fooling around with the Bios, and so forth.
Eventually I got the idle temp down to 37 degrees, and with a heavy
workload it can only go as high as 55 degrees.

But now the CPU fan is plateaus at 3000 rpm! It stays there even when
the CPU temp gets into the 50s. However, when the system is
sufficiently cool, the fan will slow down to the 2000 rpm range. So
the fan can slow down, but can't get faster than 3000 rpm. Any idea
why?

 

[Dave C.]

When I first built my Athlon 64 (NForce3-based) system, the system ran
pretty hot. Idle at 45 degrees, and it would often go as high as 60
or 65 degrees. The CPU fan usually started at 3000 rpms when I start
up the computer, then worked its way up to 4500 rpms after a few
minutes (and stayed there).

I fiddled around with the system, installing better drivers,
rearranging case fans, fooling around with the Bios, and so forth.
Eventually I got the idle temp down to 37 degrees, and with a heavy
workload it can only go as high as 55 degrees.

But now the CPU fan is plateaus at 3000 rpm! It stays there even when
the CPU temp gets into the 50s. However, when the system is
sufficiently cool, the fan will slow down to the 2000 rpm range. So
the fan can slow down, but can't get faster than 3000 rpm. Any idea
why?

Fan is dusty, or just plain wearing out. Is it sleeve bearing? -Dave

 

[David Maynard]

When I first built my Athlon 64 (NForce3-based) system, the system ran
pretty hot. Idle at 45 degrees, and it would often go as high as 60
or 65 degrees. The CPU fan usually started at 3000 rpms when I start
up the computer, then worked its way up to 4500 rpms after a few
minutes (and stayed there).

I fiddled around with the system, installing better drivers,
rearranging case fans, fooling around with the Bios, and so forth.
Eventually I got the idle temp down to 37 degrees, and with a heavy
workload it can only go as high as 55 degrees.

But now the CPU fan is plateaus at 3000 rpm! It stays there even when
the CPU temp gets into the 50s. However, when the system is
sufficiently cool, the fan will slow down to the 2000 rpm range. So
the fan can slow down, but can't get faster than 3000 rpm. Any idea
why?

Doesn't need to run full speed because the case cooling is better.

 

[Opticreep]

Doesn't need to run full speed because the case cooling is better.

Nah. It was running at 4500rpm when the cpu was idling at 45 degrees
before. Now, the CPU can go as high as 50 degrees on a heavy
workload, and the fan is still stuck at 3000rpm.

It's a month-old fan, so I don't think there's any defects on it.

 

[David Maynard]

Nah. It was running at 4500rpm when the cpu was idling at 45 degrees
before. Now, the CPU can go as high as 50 degrees on a heavy
workload, and the fan is still stuck at 3000rpm.

The fan's sensor isn't the one giving you the 45 and 50C reading.

The numbers you originally posted suggest the case temp went down by as
much as 10C. Fan doesn't need to run full speed.