The so called pwm line uses the pwm mechanism to adjust the fan speed and the fan voltage is constant avoiding the control voltage to shift.
Difference between 3 pin and 4 pin fan connectors.
The 4th pin sends a signal to the fan to change speed allowing the fan to run slower and.
2 pins provide electricity to turn the fan.
With a three pin connection two are voltage and one is a speed sensor.
A 4 pin pwm fan connector will have four square holes on the front and four wires entering the back.
Changes can easily cause the fan to stall or modulate erratically if the voltage isn t correct.
The pwm control wire will not be connected so the fan speed cannot be controlled.
Chassis and processor fans use either a three wire or four wire connector.
3 pin fans or dc fans are typically worse than 4 pin fans when changes are made to the voltage in order to adjust the speed of the fan.
Line up the guides on the connector to the tab on the socket.
4 pin fans or pwm fans don t have this issue as the 4th pin on the fan allows voltage changes to be made more quickly and less erratically.
The pwm fan does not need to rely on the motherboard bios which is more convenient.
Most motherboards have 4 pin for the cpu.
A 3 pin fan connector will be smaller in size than the 4 pin pwm fan connector.
It will also have three square holes on the front and three wires entering the back.
Connecting a 4 pin fan to a 3 pin socket.
A motherboard controls speed by intermittingly sending a current pulse to the fan.
The 4 pin cooling fan is based on the 3 pin and has a pwm line pulse width modulation.
The three wire connectors are for small chassis fans with lower power consumption.
The 3rd pin feeds rpm information back to the motherboard.