QUICK FIX FOR NOISY CPU FAN

Dells use temp controlled auto sped adjusting fans.  You might want to check to see if you have a process running that is using heavy CPU usage if that's the case the fan will be loud.  The performace tab of task manager will tell you the CPU usage.

Silver is perfectly correct about CPU fan noise increasing according to CPU load. But in my case, the fan noise often increased when the PC wasn't under load and remained quiet when at almost max CPU load (burning DVDs and running other applications.) I guess that running the Dell diagnostics check blew some of the cobwebs out of the CPU fan.

 

 

The 'cobweb' notion might be close to right.  Dust buildup can/will retain heat and make the fan run faster.  But just running 2500 RPM 5 times for 10 seconds is not going to change dust buildup.

 

'Noise' can be fan speed, can be rattling/vibration, can be impending bearing failure.  'Exercising' the fan might have a temporary impact on the latter two.  I think you'll find you have altered the symptom but not solved it.

 

To be certain the noise is coming from CPU fan, when it's happening stick a Q-tip through the case holes into the fan and stop it temporarily.  If the noise continues, odds are better it's another rotating part (display card fans are notorious) or resonance.

Good addition Geoff.  A recent post noted that the owner had a longhaired cat and all the vents clogged with cat hair regularly.

 

Running the fan fast, as in the test, would clear out the backlog of case heat and allow it to slow down until the heat built back up, in the case of a partially-clogged intake.

I suggest you check the air intale at the front of the computer Mine was blocked with dust etc after clearing the fans have gone back to normal