PC Tower fan cycling|?

[The Medway Handyman]

The cooling fan on my PC tower has started behaving oddly.

Instead of coming on for a while , then switching off, it comes on for 2 seconds, off for 10 seconds, then on for 2 etc.

Any thoughts?

[AlanC]

It might be that the cpu heat sink is clogged up with dust. Most modern systems monitor the cpu temperature and speed up the fan if it starts to get to hot. This normally happens when the cpu is being used heavily but if its happening when the cpu isnt busy, it might indicate that the air flow is beiing restricted.

Alan

[John Rumm]

Its unusual for a fan in a tower to cycle at all. The vast majority run continuously. More modern ones will run continuously with speed control, where the speed is proportional to the temperature.

Does the BIOS settings screen have any hardware checks? Many have a page that reports voltages, temperatures, and fan speeds. You need to push "Del" at early startup to get to the BIOS screens - that will work for most generic PCs. Branded boxes like hp etc may well have a different key - often one of the funtion keys. They normally tell you which on the early boot screen.

[Alan]

In message , The Medway Handyman wrote

The fan, CPU heat-sink or filter is full of dust?

[Robin]

Make and model might help. (When you say "Instead of coming on for a while , then switching off" it has possibly been coming on at full speed when booting up, then dropping back to slow speed which may well be ~silent.)

[Andy Burns]

From the symptoms, my money's on HP/Compaq/Presario ...

[therustyone]

First thing is to check if the CPU is actually overloaded. Go into task manager (CTRl+Alt+Del) , click the performance tab and read what CPU usage says. If it's more than 50% it's a software program (possibly malware) that's hogging the CPU and overheating it. If it's only around 5% the fan is probably blocked as others have said.

rusty.

[Invisible Man]

If you need to clear dust the best way is with repeated short blasts from a can of compressed air.

Some PC components are very sensitive to static. If you need to open up the case and do not have an earthed wrist band keep one hand on a metallic part to. Vacuum cleaners can be a static risk.

Towers at floor level near carpets may need a quick blast of air every 3 to 6 months.

[Robin]

A good starting point but I have found CPU heatsinks which needed *much* more than compressed air to lift densely matted fibre from between the fins. A cotton buddy if it fits (or reversed if they are the bendy plastic ones). I suspect the presence of one or more cats militates for quicker and denser matting. But even then I can't recommend an angle grinder as a solution: apart from anything else, they move too fast :)

[The Medway Handyman]

A clairvoyant computer expert :-) Spot on!

Usually leave the beast on 24/7. Turned it off last night & this morning its back to normal.

[John Rumm]

Unless its running a particularly "hot" processor, then normal behaviour on these is a burst of full speed fan on power on, and then it should quickly fall back to significantly quieter and slower operation. This is a newish PC IIRC? It could be that you are seeing the effects of a rise in ambient temperature (probably exacerbated by dust - especially if it sits on the floor) causing it to trip of the high temperature threshold that causes it to demand max cooling.

[John Rumm]

"overloaded" being subjective term here and nothing to get worried about in hardware terms. 100% load 24/7 should cause the machine no damage, even though it would be atypical for a machine apparently doing nothing.

[Andy Burns]

They do have a tendency, once they get too warm, to start cycling the fan, I generally notice the annoying noise pulsating.

What's the exact model (preferably from the small-print on the label, rather than the badge on the front) some can be fixed with a firmware upgrade, others you either need to improve the airflow around the outside of them, or as others have said, if they are clogged up, clean the dust out, sometimes re-arranging cables internally can make the difference.

[Bob Eager]

Be careful with fans, as compressed air can actually overspeed them.

[Mr Pounder]

Take the sides off the tower system and use a paint brush to clear all the dust out. I do mine every 6 months, there is always a lot of crap inside.

>

[Andrew Gabriel]

Cycling on and off IME is due to fan bearing lubrication having gone sticky. Fan runs, cools it's lubrication down, which goes too thick and stops fan. Fan self-heats, melts lubrication, and starts running again. Cycle can be anything from about 10 seconds to a few minutes, depending how bad the lubrication has gone.

Does the fan spin freely by hand when it stops rotating? If not, you need a new fan.

[Ian Jackson]

In message , Andrew Gabriel writes

As others have stated, every few months or so, it's important to check - and, if necessary, clean out - all the grot that accumulates in your computer. Cooling fans and hear sinks simply don't work if they get clogged up.

I'm another one who has had trouble with the power supply extractor fan. I thought the computer was running a bit on quiet side, and I found that the fan had seized up absolutely solid - so solid that I simply couldn't budge it at all.

As it was not immediately convenient to get a replacement, I decided to try and free it off - which I eventually did with the help of the tip of a hot soldering applied to the spindle (visible at the bearing end after a sticky label had been removed). I then worked some WD40 into the bearing, and the fan then spun freely again. After testing the fan for a few minutes, I replaced the sticky label (after cleaning off any extraneous WD40, of course).

The fan subsequently ran happily for the next couple of years, but then I thought it might be prudent to re-oil the bearing with some 'proper' oil (this time, 3-in-1). Two years further on, and it's still going.