A CPU cooling fan is a dedicated fan which cools down the heatsink and eventually the CPU (Processor)
The CPU and GPU cooling fans connect directly to the motherboard via a cable running from the fan. When CPU and GPU chips get hotter, the cooling fan spins faster.
COOLING FAN LOCATION IN A LAPTOP.
On some laptops the cooling fan can be easily accessed through a door on the bottom, as on the following Gateway laptop.
If you cannot find it on the bottom, then it’s buried inside the case, as on the following Dell laptop.
COOLING FAN RELATED PROBLEMS.
If your laptop feels very hot and shuts down without any warning, it’s possible that you have a faulty fan. Listen for the fan. Is it working? Sometimes you can see the fan through the fan grill on the bottom of the laptop. Can you see the fan spinning?
If the fan never starts, probably it is bad and has to be replaced.
When the fan bearing goes bad, the fan starts making grinding noise. In this case you’ll have to replace the fan.
If your CPU fan works hard all the time, most likely it happens because the heatsink is dirty and is clogged with dust and lint. You can clean the heatsink using compressed air.