Laptop fan stopped working, but spins for one second after turning off PC

I have Dell Latitude 5840. Yesterday I pressed o on the keyboard to hard. I heard some scratching sound and then silence. Basicaly my fan stopped working. I tired some monitoring software and all is showing 0 rotations. But Im sure the problem is not in mechanical damage of the fan. When I turn off the PC the fan spins for a second and then stops. What can be the issue?

Question by plomba on Super User, licensed CC BY-SA. We show a short excerpt and link to the original thread as credit.