I bought replace fan for the psu and when i connect it to the unit it wont spin, i dont know why. When i connect it to the motherboard it works properly. Can i install it in the psu and pull out a wire and connect it to the motherboard?
Does the fan have the same characteristics as the old one? Does the old one still work or did it stop spinning? The PSU fan should be controlled by the PSU itself, but if you bought the correct fan and the old one also won't spin, then the circuit controlling the fan may have failed.
Some PSU's do their own fan's speed control internally. This means the fan does NOT start up right away, but does start a bit later when the PSU warms up.
Try this test. Re-install the old fan and wait until the PSU is cool. Turn things on and watch that PSU fan right away. If it starts right away, your PSU is not waiting for it to heat up. But if it stays off for a while and then starts, that is exactly what your new fan will do, also, when you install it.
Unless you have a crappy PSU, the fan should spin only as fast as it needs to. It should spin at full speed only when the PSU needs it; otherwise it probably will be noisy.
Old fan: 85.2 CFM (145 m³/h), 0.37A, 4.44W
New fan: 93,4 m³/h (55 CFM), 0.05A , 0.6W
While the new fan definitely is quieter, that's a significant difference. If you never use that PSU close to it's rated output, then it may work. Personnally I would install a quieter fan having similar characteristics.