Wondering about my PC fan

[Art]

From your website, Giorgios, I see that I have a 3-wire 12VDC power fan on my PC.    I understand the yellow wire is probably a signal that uses a Hall effect sensor to modulate the fan speed.   

The fan often stops.     If I hit its blade with a spurt of compressed air, it starts spinning again, but then stops a few seconds after I release the spray-can trigger.    Do you know of any way I can tell if the fan stops because the sensor is bad, or because the fan axis is clogged with dirt?
The room temperature is 25 deg.C.   So I think the fan should be rotating.  But it's not.
I am wondering if I need to replace the fan.  I already removed the panels from my PC so the hot air doesn't build up.

-Art

[kam]

It could be that the controller is bad. Or the hall sensor. Some controllers have this feature to stop the fan if they detect no rotation, to save the coils from overcurrent and destruction. So if it is ever clogged it will not be destroyed. In that case, if the hall sensor fails, the controller will think that the motor is blocked so it cuts the current.

In any case, yes, you need to replace the fan