Cooling fans are once again a physical moving part that often dies
from heat failure. Typically the bearings will dry out or become dust
caked and will not spin on their own.
Identifing the Failure
1) Does the fan either takes a bit of time to start spinning, or needs
a "hand start"?
If this is the case the fan simply needs to be greased up.
2) Does the fan sit idle, or spin down when "hand started"?
Most cooling fans contain a permanent magnet and an electromagnet. The
electromagnet switches between north and south, the permanent magnet tries
to follow. As the power being pumped into the electromagnet is fairly weak,
they will fail in time.
To repair they normally only require being taken apart, and greased.
Once they've been greased up, they should work normally.
Article by Slam, Last Updated June 2004
Test if the fan has continuity, if not there is a good chance a
wire in the electromagnet is broken, in which case you're either
replacing or re-winding the fan (in which case you're on your own,
as I feel this is not worth the effort)