Testing your computer's cooling system

To test your cooling system, first take the PC’s case side off, then check that all the fans are spinning and that they appear to be blowing air in the right direction. Load a temperature and fan utility, so you have a display of CPU temperatures and fan spin rates.

Many motherboard manufacturers now supply these utilities for their motherboards. Hopefully, this will have a logging feature so you can record the data for later analysis in a spreadsheet.

Third-party temperature utilities may give more information, or be more flexible in their configuration. Motherboard Monitor (MBM5) by Alex van Kaam and Speedfan by Alfredo Milani Comparetti from are good examples.

Such utilities may also be able to control your fans – depending on your motherboard – and report the condition of Smart-capable hard disks, for which information including temperature will be available.

Motherboards often include on-board temperature sensors or connectors for external thermocouples. For AMD processors, there is often a sensor underneath the CPU socket, and older Intel processors include a temperature-sensing diode.

Intel’s most recent chips include multiple digital temperature sensors. It’s the signals from these sensors that the Bios and monitoring software read. These sensors may be inaccurate, so it’s wise to allow for a margin of 5º or even 10º when looking for potentially dangerous temperatures.

Once you have checked that all the fans are running correctly and that CPU temperatures aren’t too high, replace the side of the case and add the temperature utility, with logging turned on, to your Startup folder. Turn the PC off and let it cool for half an hour. Turn it back on and leave it running in idle for 20 minutes, then run a processor-intensive task for 20 minutes.

Stop the task and leave the PC running for 20 minutes. Stop the temperature logger and examine the file by graphing the results using a spreadsheet (see attached pdf temperature plots).

As a rough guide, the maximum operating temperature for most CPUs is between 90-100ºC. Normal running temperatures should be no more than between 60-70º C and with a top-notch cooling system you should see a temperature of around 45ºC.

If you have problems, it’s worth checking the airflow. Air is a little difficult to see, so the old-fashioned smoke-stick test is quite a useful way of checking what your airflow is doing.

A stick of cheap, smoky incense works well. Used on a test PC, we found that virtually no air was entering through the rather restricted front lower grille and that one of the case fans was generating a lot of turbulence in conjunction with the power supply fan.

See also Creating a computer cooling system and Cooling technologies explained