Tricking laptop into thinking that fan is running.

[iBlaze]

So i have a old laptop that i use as a virtualization server. I took it apart so there is only the motherboard remaming and some other stuff. How would i trick the laptop into thinking the fan is running when it is not?
Btw i have 2 much bigger fans right next to the laptop fan, the reason why i want to do this is the fan making a scratching noise and i cant be bothered to fix it.
There are 4 wires from the fan :

Thank you in advance!