Have you ever had a PC that started making strange whining noises? Even if you've investigated the cause of the noises, which can often sound pretty serious when you hear them, you may not realise the reason for them. The chances are they're caused by a cooling fan with dust in its bearing.

Fans are one of the few components in a PC which have unsealed moving parts. By their nature, they have to be open to the air to suck heat out of the machine and push cool air in. As a result, they're extremely susceptible to all the airborne particles that make up household dust.

Contrary to popular myth, household dust is not primarily composed of human skin. In fact, although there are some skin cells present in virtually all house dust, its composition varies quite dramatically from area to area, season to season and room to room.

As you might expect, it includes pet hairs, pollen, plant seeds and broken-down insect remains, as well as lots and lots of particles of dirt. Both the organic and inorganic components of house dust can be troublesome to a machine with moving parts. Minute fragments of minerals can become trapped between bearings and shafts, while a build-up of softer material can act as a brake and slow a fan's rate of rotation.

Thankfully, with a little DIY work on a typical desktop PC case, you can increase the reliability of the fans, which in turn ensures proper cooling of all your system's important components: processor, video card, memory and power supply.

The simple answer to fan failure is to filter the air that enters your PC. Doing this isn't difficult at all, and here's a really simple way to cut out the muck.

1. Find a filter

The obvious filter material for a PC intake is that used for screening dust in a vacuum cleaner filter pad, since this material is designed expressly to perform this function.

filters

These filter pads are cheap and readily available from all good electrical shops, and since you'll mark out and cut the filter material to fit your particular PC, it doesn't matter which vacuum cleaner model filters you buy.

You're after the largest area of filter you can get for your money, though, so go through the different models. You may be able to buy filter material in sheets, which could be even cheaper. It won't be a major outlay: you're typically looking at spending just a few pounds for a bag of filter pads.

2. Hold it in place

To get started, you'll need to find something to hold the filter material in place over the intake on your PC's case. You could stick it in place, but that would make it hard to replace periodically. Fortunately there's a ready-made holder for the filter material in the form of a simple J-shaped plastic extrusion.

Holders

This kind of extrusion is normally used to hide the rough edges of hardboard or acrylic sheet fittings, but it's just as good for holding vacuum filter material, and the gap is ideal for use as a slide fit. It's available in strips from DIY chains like B&Q and Homebase for a couple of pounds a metre.

You should be able to get all the lengths you need to add filters to a typical PC from one extrusion pack. Measure the size you need to hold the filter material in your PC and cut it to length with a craft knife.

In most cases, two strips placed at the top and bottom of the filter will work best, but for small areas a single strip may suffice. You can attach the strips of extrusion to the case with double-sided tape, applied first to the extrusion and then to the PC's case. This tape is readily available from most DIY stores.

3. Cut the filter to size

Measure the ventilation holes in your PC's case and cut out a cardboard template for each. Lay each template on the filter material and draw round it with a marker to make the inserts. Keep the templates, so you can renew the filters every so often.

Cut filters

You can fit filter pieces to the fan ports on power supplies and hold them in place by undoing the mounting screws and screwing them back through corresponding holes in the filter material.

Cut the filter material with scissors – a craft knife tends to snag. Though it's generally an unwoven, felt-like material, filter pads can still be cut into quite intricate shapes if needed.

4. Fit it to your PC

Fitting the filters, once you have the extrusion and filter material cut to size, is very simple. Stick the extrusion strips to the top and bottom of the case vent and slide the prepared filter strip between them so they're gripped in the channels.

Fit filters

Filters can be added inside or outside the case, whichever is more convenient (the result will look neater if they're added on the inside, of course). Try not to stick the extrusion over holes making up part of the case vent.

Adding the filter will reduce the airflow through the vents in comparison with unfiltered vents, but not significantly – a fan running slowly because of dust in its bearing will suffer far more.

5. Change it regularly

If all this Blue Peter-style DIY seems like overkill, it's worth mentioning that your author, who runs three working PCs pretty much continuously, was replacing a fan roughly every four months between these machines. This is in a domestic rural environment with few vehicle fumes or other typical urban contaminants to clog the workings up.

Before and after

Since installing filters and nano-ceramic fans, not a single fan has had to be replaced and all are continuing to run quietly and provide specified levels of airflow. Changing the filters on each PC takes around 10 minutes to cut the material to size and another 10 minutes to fit. That's just 20 minutes every six months, probably less time than it typically takes to download and install a Service Pack.

Look at the used and fresh filter elements in the picture here and you can see that the filter's pretty effective and catches a lot of dust that would otherwise end up inside your PC.

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First published in PC Plus Issue 289

Liked this? Then check out How to make a laptop cooling stand

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