4 pin fan, 3 pin header

Hey all, got a question. I recently got some older (3-5 yrs) Dell PCs. One has a dead CPU fan. It is an 80mm (I believe) that connects to a 3 pin header (+, -, temp or speed control) Wire colors are red, black, white. In another Dell, I have the same size fan, but it has 4 wires (+, -, temp, PWM/speed control).

Now I know I don't get the benefit of speed control when using the 4pin fan on the 3 pin header, however, when I plug it in and turn the PC on, the fan spins at it's highest speed. For this configuration, I did not connect the blue wire, which I believe is the speed control. The thing sounds like it's going to take off.

The questions I have are: Is there a way to turn down the speed of the fan? Should I hook up the blue wire instead of the yellow? Should I just spend the $10 and get a 3 pin fan? (was trying to avoid hitting a store.. weather sucks out there). Any other suggestions?

Thanks...

Lee

you need voltage control on your mobo either way

Do not switch the pins around, it will do nothing.

3 pin fan headers are voltage, ground and RPM speed detection, not control.
4 pin fan headers are voltage, ground, RPM speed detection and PWM speed control

As m0r71f3r said, if you want speed control, it has to be through voltage.

OK. So I'll just go get another 3 pin and save the 4 pin for the system I pulled it from.

Thanks for the assist.

Hmm...never actually considered it, but can you undervolt a PWM fan the same way as classic 3-pins?

Omsion said:

Hmm...never actually considered it, but can you undervolt a PWM fan the same way as classic 3-pins?

Click to expand...

Yep, it's still a motor, 7v and 5v mods are still viable.

If its a thermally controlled fan (Dell likes to use those) and you put a regular fan in its place you still wont have fan speed control. I learned this the hard way.

Does it give the error during boot up about the fan, so you have to press an F key to get it to boot up?