Difference between 3 and 4 pin fans

[chedderslam]

What's the difference? I've seen both. Can I just connect the 3 pins on a 4 pin fan?

 

[creecher]

the fourth pin just controls the speed. if its not connected, the fan will just automatically run at full speed. none of my 10 fans have the it controlled. on some extreme high-speed fans, they will have a 4 pin molex that plugs into the PSU, and 1 wire will run to a 4 pin fan connector, so they it will have 1 cable for power and the other for speed control. they do this because they pull more electirictiy then about 99% of fan controllers or motherboards can handle.

so the answer to your question is yes.

 

[Know Nuttin]

the fourth pin just controls the speed. if its not connected, the fan will just automatically run at full speed. none of my 10 fans have the it controlled. on some extreme high-speed fans, they will have a 4 pin molex that plugs into the PSU, and 1 wire will run to a 4 pin fan connector, so they it will have 1 cable for power and the other for speed control. they do this because they pull more electirictiy then about 99% of fan controllers or motherboards can handle.

There are various ways a board can control the speed of the fan. The use of the 4th lead (PWM) is one. Other's lower the voltage to lower the fan speed. When a molex and a single wire fan pin header is used on a fan, the fan pin header is normally for rpm monitoring and not for fan speed control.

You can use a 3pin fan on a 4pin fan header, you will notice that the "key" on the board fan header is fitted in such a manner as to allow you to plug in a 3pin without any issuue.