Windows 7: CPU fan running fast

I swapped out a CPU in an old machine (XP) today and on starting the machine the CPU fan kept running at full speed.


I swapped the CPU (Pentium 4 @ 3.2Ghz) again with another known good one (Pentium 4 @ 3.0Ghz only difference is the L2 cache size) to check if the CPU was the problem but it still runs at full speed. The heatsink itself is almost stone cold even after half an hour's running.
I used fresh thermal compound each time (Noctua HT-N1) after thoroughly cleaning / preparing the two surfaces.


I have Googled to see if the fan itself could be at fault but cannot find anything related to it.


Have also checked the BIOS and the fan speed is enabled by which I take it that it will run at whatever speed is necessary for the CPU temperature?


So unless the fan itself has a controller / sensor (Intel) I don't know what to check next apart from finding another fan to put onto the heatsink.

Does anyone know of a check I can do with a multimeter or an app for instance on the fan to check it's operation?

Meant to mention the board is a Intel 915GAV.

Have you tried putting the old cpu back in to see if the fan runs at full speed?

How many leads does the fan connector have? AFAIK, only those with 4 leads are able to vary their speed using PWM (Pulse Width Modulation). This signal is available on the 4th pin, the other 3 being Ground, +12V, and RPM output.

If the fan connector is a 3 pin and if it will reach try connecting it to the fan connector above the PCI-E slot.

The heatsink may be cool but that isn't what controls the speed. What is the CPU temp?

Does this say enabled or just shows the fans RPM?

Do you have these options?
Don't know if this is your problem - Desktop Boards - Thermal zone information
With the risk of killing the motherboard I would not attempt to update the BIOS until you have exhausted all other options.

Yep the fan/s (have tried an exact same cooler unit) have four leads both genuine Intel.

Yep have tried the original CPU back in.

The BIOS only shows me CPU fan control [enabled] / fan control > [enabled] / Lowest fan Speed [Slow]

Processor zone 56C
Processor fan speed 2756rpm > original cooler unit

Processor zone 60C
Processor fan speed 2056rpm > other cooler unit

Now the thing boots and runs real quick for an older machine and there is no problem with running apps etc The only thing is that the CPU fan runs flat out and is kind of really noisy.

Am just wondering if I should reset the BIOS by jumping it or taking the battery out or just picking default settings.

Maybe I have two dud CPU's?