My fan always spins very slow. It spins fast when CPU temperature increases significantly.
Try furmark or some application to stress the processor and see if the fans kicks in?
Also, you can remove the fan, remove the sticker and a rubber cover beneath it, put 2 drops of machine oil or trimmer oil, place the rubber and sticker back.
The bearing might be out of oil.
I do this with all the fans of my PC.
Watch this - *www.youtube.com/watch?v=fgwX6fQTqCk