Laptop fans expel air and make a soft to moderate audible sound under normal use. If your laptop's fan is silent, the air near the vents is calm and the laptop is very hot, it's likely that the fan is not working. Laptop cooling fans play a crucial role in laptop longevity and functionality, and an overheated system doesn't work well, if it works at all. Make sure to replace a broken fan immediately to prevent hardware failure.
Watch for Errors
If the computer regularly restarts without warning, slows down to a halt in normal use or gives you the dreaded BSoD, or Blue Screen of Death, there may be a problem with the fan. The fan itself is attached to a heatsink as part of the cooling unit, so even if the fan is blowing air, there can be a problem with another part of the unit. Your system may overheat if the cooling unit comes loose or the thermal compound that bridges the CPU and the cooling unit wears out.