Your Acer Extensa uses a fan to cool the central processing unit so that it doesn't overheat and sustain damaged. The fan speed is set with "Smart Fan Control," which automatically adjusts the fan speed depending on the temperature of the CPU. This means that your fan isn't running all the time. This can make the computer quieter but more likely to get hot. You may turn this setting off, so that your fan will run all the time, from the basic input/output system menu.
Start, or restart, your Acer Aspire laptop.
Hold down the "F10" key while your computer is starting up to load the BIOS menu. Here you may move around using the arrow keys, and press "Enter" to select the highlighted option.
Locate the "Fan Settings" options page. The fan settings will normally be located under the "Hardware Monitor" or "H/W Monitor" menu. This may vary, however, with the Aspire series.
Select the "Smart Fan" option and use the arrow keys to change this to "disabled." This will mean that your fan will run constantly at full speed. If you want to lower the speed then lower the voltage using the "CPU Fan Voltage" setting.
Select "Save Settings and Exit" and you will be returned to the BIOS menu.
Select "Exit." Your laptop will restart and from now on your fan will run all the time.