Connecting a DC computer case fan to your computer system is a relatively straightforward process, but there are different methods depending on the motherboard and the fan's design.

The most common connection is through a 3 - pin or 4 - pin fan header on the motherboard. A 3 - pin connector has pins for power (usually +12V), ground, and a tachometer signal. The tachometer signal allows the motherboard to monitor the fan's speed. When connecting a 3 - pin fan, simply align the connector with the corresponding 3 - pin header on the motherboard, making sure to match the pin - out markings (usually indicated by a small triangle or color - coding).

A 4 - pin fan connector adds a PWM (Pulse - Width Modulation) pin. PWM technology allows the motherboard to control the fan's speed more precisely. By varying the duty cycle of the PWM signal, the motherboard can adjust the fan's speed according to the system's temperature. Connecting a 4 - pin fan is similar to a 3 - pin one, but it offers the added advantage of better speed control.

Some high - power fans or cases with multiple fans may also use Molex connectors. Molex connectors are larger and typically provide more power. They are often used when the motherboard's fan headers are not sufficient to power all the fans or when a fan requires more power than the motherboard can supply through its headers. To connect a fan using a Molex connector, you need to find a free Molex connector from the power supply and plug it into the fan's Molex socket.