Will a CPU fan work on a chassis fan plug?

It wont be a problem, I have also done this because it allows me to control the fan inside of windows, which I could not do with the 3-pin connector.

Double post, sorry.

Heatsink fans come in both forms 3 or 4 pin.
The 3pin connector is notched and should work fine in the 4pin cpu_fan header.
I use a 3pin in my cpu_fan header no problem.

http://www.intel.com/support/motherboards/desktop/sb/cs...

On a three-pin fan, the pins are for (1) ground, (2) 12v and (3) speed indication (in BIOS or Windows). The 4th pin allows speed control or PWM (pulse-width modulation, a means of controlling speed on DC motors). If you connect a 3-pin fan to a header that's not labelled for your CPU, you'll be fine as it'll just spin, although if BIOS isn't detecting CPU fan speed (with your fan connected to the chassis fan header) I'm surprised it's not throwing up an alert. Guess that depends upon the BIOS / mobo manufacturer.

Thanks for all the replies. I found them very helpful. I was able to plug the CPU fan into the four pin connector because the slot is off-centered to allow for it. I hadn't noticed that before. This particular mobo has a program that lets you monitor the speed and temp of the cpu and mobo from windows, which is nice.