If you think the inside of your computer is heating up too much and all is apparently OK regarding the position of the processor and, mainly, of its fan, as we have seen in previous pages, there are some ways to improve the computer’s inner cooling.

The cheapest way is to open holes in the power supply on its lower side, that is, the side facing down when the computer is stood up. You can also make openings in the plating facing the case’s 5 1/4" bays. These openings should only be made if originally there are no holes for expelling hot air on your power supply.

To these holes you must first unplug the computer from the power outlet, remove the power supply from the case and open it, making the holes with the plating separated from the power circuits, to prevent metal falling into the circuits, thus causing a short circuit when the computer is switched on. These holes will let hot air out easier from inside the case, following its natural path, the power supply.

You can also install auxiliary fans inside the case. Such fans are easily found in computer shops (ask for 80 mm auxiliary fan), but you can also save money by using a fan removed from an old power supply (for instance, belonging to a scrapped computer). If you intend to cannibalise a fan, be careful. Older power supplies, used in desktop type cases (from the XT and 286 age) use 110/220 V fans that cannot be reused. You must use 12 V fans, utilized in the majority of power supplies applied in mini tower type cases.

The auxiliary fan can be installed in two places in the case. The most usual place is under the hard disk drives bays (see Figures 5 e 6), where the system intakes cool air. Be very careful when seating the fan in this place, as its position in the ventilation flow must be drawing cool air from outside to inside the computer. Every fan bears, on one of its sides, an arrow showing the airflow direction. This arrow should, therefore, point towards the inside of the computer.

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Figure 5: Place for installing an auxiliary fan inside your case.

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Figure 6: Another angle from this place.

The second position is not found in all cases: it lies in the space between the power supply and peripheral cards, on the back of the case. In this case, the fan should be installed in the exhaust direction, i. e., blowing hot air from inside to outside the computer. The fan’s arrow must therefore point out the computer.

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Figure 7: Another place for installing an auxiliary fan. Not all cases have this spot.

You must get the direction of the fans’ air flow right, as if you get it wrong the computer may heat up more, definitely not the intended outcome. The rule is very simple: fans at the computer’s rear should be fitted in the exhaust direction (inside to outside), while fans in the computer’s front should be fitted in the cooling direction (outside to inside).

Newer fans sold at outlets have three wires and a plug for connecting to the motherboard via a connector called "Chassis Fan", "Aux Fan" or something like this. On the other hand, older fans have two wires and should be connected directly to the power supply via one of the plugs for 5 1/4" units. If you intend to use a cannibalised fan, note that its black wire should be connected to the supply’s black wire, but its red wire should be connected to the supply’s yellow wire, its 12 V output, and not to its red wire, as could be assumed (the red wire is its 5 V lead). The extra wire on newer fans is intended to measure the rotating speed and, according, inform the motherboard whether the fan is working properly or not.