I am doing a build with a corsair 800D case, P6T Deluxe V2 and Corsair Airflow fans. The three fans that came with the 800D use 3 pin connections and so does the Corsair Airflow. The motherboard only accepts one cpu fan (cpu_fan), three chassis fans (cha_fan) and a power fan (pwr_fan). I don't imagine I can use (or at least, it wouldn't be a good idea to use) the pwr_fan on the Corsair Airflow so I'm not sure where to connect it. Would converting the 3 pin to a 4 pin molex and connect it straight to my PSU?
The factor that determined where we connected them was the
length of the cable: that ended up being the pwr_fan header
on most of our motherboards, because it was within reach
of the cable provided.
You want a 3-pin header so your motherboard can detect
the fan rpm. With ASUS motherboards, a Windows program
called PC Probe II permits graphical display of fan speeds,
voltages, temperatures and such.
Yes, you should be able to "hot-wire" a conversion from
3-pin to 4-pin Molex: the middle pin on the 3-pin header
is a +12V conductor. The other two are GROUND and
ROTATION in rpm.
Check your motherboard User Manual for the pin assignments.
The only problem with your conversion idea is that
we have experienced this Corsair memory fan run too fast
until the BIOS takes control, using the ASUS Q-Fan feature.
Thus, to eliminate the noise caused by excessive rpms
we had to enable Q-Fan and adjust the maximum rpm
downwards in the BIOS: then the noise at POST went away.