Some ATX cases are coming out from production line with a very serious problem. The power supply fan, that removes the heat generated by PC components, is inverted. As a consequence of this faulty installation of the cabinet fan, PC overheats and causes several errors in the PC, like freezes, halts, random resets, excess of General Protection Faults errors (This program has executed an illegal operation and will be closed) and much more.

In the mini-tower case, airflow is forced by the power supply fan working as an exhauster, that is, removing the air from the PC. Just as discussed in school classes, warm air rises up and the cold moves down. Therefore, the air that is warmed by the PC components (motherboard, processor, RAM, etc) goes to the top of the case. By means of the slots existing in the power supply, this air goes out of the case with the help from the fan. Consequently, cold air comes in automatically through the slots made in the case front panel, creating a constant and inevitable airflow, as you can observe in the figure.

In case where the fan was wrongly installed, the air, instead of going out, comes in. Therefore, the warm air from the case has no way out (as warm air natural trend is to raise up), creating an overheated spot in the case, as you can see from the illustration. You'll notice that in those faulty cases, the CDs that are inserted in the CD-ROM drive stay warmer than normal. PCs installed with the inverted power supply fan present several problems due to the overheating.

Identifying a case with this problem is a very simple task. Just place your hand in front of the power supply fan with the PC powered on, and feel whether air flow is coming in or going out. If correct, air flow should be going out (you'll feel the air blowing out coming from the PC).

In case your PC has the fan inverted, the solution is pretty simple. Just pull down the power supply and switch fan installation. In case you feel you don't have the right technical requirements to execute this procedure, call a service man to do it.

Note: If your PC is still in the warranty period, don't touch anything, as to open the case (and even more the power supply) will void the warranty. In that case, contact the dealer who sold you the PC in order to perform the repair.