My PC fan speed is jumping from slow to flat out. The cabinet is well ventilated and I have checked the grills are clear. It often starts from switch on in this state which prevents it from booting and I have found by accident that if you knock the cabinet the fan speed drops and allows the PC to boot. The PC will also not switch off when the fan is running at high speed. An added problem has developed today in that the PC freezes for a minute or two then carries on working fine.
I run XP with service pack 3, I have Zone Alarms security suite and I use Reg Cure and Pareto to keep things clean and running sweet.
I have 2GB ram on a Athlon 2.19Ghz processor.
My guess is a hardware problem but the machine is under warranty and they just tell me to run a recovery and will not accept that by the nature of the symptons I does not seem to be a software problem.

The first thing I'd do is check the Internal (Motherboard)connection to the fan
The surging and (goes better when knocked) may be the connector is not pushed into the socket fully (is a snug fit)


I posted this the other week in the UK
about monitoring the Fan Speeds and much more
Install it and you'll be able to pinpoint the root cause

quote:

If you want to keep an eye on the Temps inside your Computer install www.almico.com/speedfan.php its a 1.75MB download (freeware)
Also has several functions besides. It can be used to turn up/down the Fan speed/s (If you have a game Playing) It also says it can be used to alter the FSB Speed slightly (advanced users only) Will be of help if you have a High end Machine

quote:

SpeedFan is a program that monitors voltages, fan speeds and temperatures in computers with hardware monitor chips. SpeedFan can even access S.M.A.R.T. info and show hard disk temperatures. SpeedFan supports SCSI disks too. SpeedFan can even change the FSB on some hardware (but this should be considered a bonus feature). SpeedFan can access digital temperature sensors and can change fan speeds accordingly, thus reducing noise. SpeedFan can find almost any hardware monitor chip connected to the 2-wire SMBus (System Management Bus, a subset of the I2C BUS) and works fine with Windows 9x, ME, NT, 2000, 2003, XP and Windows Vista. It works with Windows 64 bit too.

I had a Case Fan which did the same as Trevs just a few weeks after this topic was Posted and I Found there was hair/fluff wrapped around the Fan pivot causing a "braking" effect when Cold yet Starting to surge when the motor warmed up and eventually running if a bit noisy
Cost of replacement fan $6 Really! (I purchased 2) and it was a Large Size...Only snag is you have to do a bit of digging to find a fan to fit the bracket. Installation is a No brainer even for a novice
Bur I had to take the Front off the Computer tower 6 toggle Clips (With thin Pliers) to expose the Fan brackets! and it took seconds to remove & replace the Fan