On Sat, 23 Feb 2008 18:41:53 -0800, "Mike"
<nospam@email.com> wrote:

>The fans were getting real noisy so I decided to replace the two 80mm 12V
>fans. I bought two 12V fans and replaced the old ones making sure I hooked
>up the right colored wires together, black to black and red to red. For some
>reason neither fans worked when I turned on the computer. The computer
>turned on without any problems. I tested the new fans with a 9 volt battery
>and they worked. I even tried reversing the wiring (black to red, black to
>red) without any luck. Anybody know how I can get these fans to work?
>
>thanks
>

If these fans are very low RPM, a PSU with a fan control
circuit may not apply enough voltage to spin them until it
gets hot. If the fan have an onboard fan control circuit
themselves in addtion to a fan control circuit in the PSU
this will also keep them from working until quite hot.

The solution to either is to use different fans, short out
the thermal control (diode or thermistor) on the fan if it's
accessible (soldering the two ends of the sensor
together), or wire the fan direct to the 12V rail instead of
through the fan control circuit, fan header.