Fans spin up for no reason

[Andeh13]

My girlfriend has a 2 year old Dell that is in good condition, over the last couples of weeks the fans have started behaving a bit erratically though. Initially when she turned the PC on they would spin up to full RPM for no apparent reason, before slowing down to normal/idle speeds. Recently however they have started doing it at random, when the computer is on.

Can anyone think of what culd be causing it, or ways of stopping it from doing it? Could it be a dead temperature sensor, or excessive amount of dust?

Thanks guys

[GoNz0]

clean it out and test the cpu fan, then if you draw a blank remove the heatsink to see if the pads dried up and turned into a piece of cardboard

[TAKTAK]

Edit: ^^Exactly what GoNz0 said^^

[Andeh13]

Ill give that a go when im next there & report back, cheers guys!

[GoNz0]

i think they should spin up 100% at POST b4 the PWM kicks in, it helps older fans spin up.

[smargh]

Old Dells have a problem with poor capacitors which fail early - particularly one batch of Nichicon caps on the GX260/GX280 models. Check the ones around the CPU for bulging (the tops & sides should be perfectly flat) or leaking.

If it is them, and you have a soldering iron, I ended up buying three big boxes of some Rubycon caps for a similar Dell problem which I could post to you.