Pin Number |
Pin Name |
Description | Wire color (usual) |
1 | GND | Ground | black |
2 | +12V | Fan Power | yellow |
3 | SIGNAL | Fan RPM | green |
4 | PWM | Digital Control | blue |
The PWM signal from the motherboard sources 5V during the on state of the pulse, otherwise it's pulled to ground.
The tacho signal from the fan sinks to ground for every revolution, the input on the motherboard is pulled high.
3-pin fan and 4 pin motherboard connector compatibility:
A fan with a 3-pin power connector may be easilly fitted into desktop board with a 4-pin fan header