These are some symptoms that can be caused by cooling fans. Other components can also cause these same symptoms.

Makes a shriek or other strong noise
The food source fan is failing and needs replacement. In most cases, the entire power supply must be replaced.

The CPU fan is failing and needs replacement.
Another cooling fan, such as a case, a disc or an auxiliary fan, is failing and needs replacement.

The fan is slow or does not turn at all
The food source fan is failing and needs replacement. In most cases, the entire power supply must be replaced.

The CPU fan is failing and needs replacement.
Another cooling fan, such as a case, an album or an auxiliary fan, is failing and needs replacement ..

The PC freezes or turns off unexpectedly
The system can be overheated due to inappropriate cooling. Verify that all cooling fans are clean and work properly.