I have an Asus motherboard with 1 x CPU Fan (4 pins) and 1 x AIO Pump (4 pins).
I want to buy a new CPU cooler witch have 2 fans (4 pins).
Having on my motherboard only one CPU Fan can I use AIO Pump as well for CPU Fan ?
Why don't you just use a PWM splitter (your new CPU cooler might even come with one) and use the same CPU fan header? At least that way you could customize the fan curve of your CPU off of one header.