"Personal Computer (PC) or Laptop Shutting Down Randomly"

By Ron Stultz

20 February 2011

Summary: random personal computer (PC) or laptop shutdowns are usually caused by the CPU chip becoming so hot, it shuts the entire system down to protect itself from heat damage. The causes of poor CPU chip cooling include: poor air circulation around cooling fans; fan clogged with debris; fan not turning or poor thermal transfer between CPU chip and cooling fan.

Background:

The central processing unit (CPU) chip of all personal computers (PCs) have millions of elements in them that give off heat.

All CPU chips have a built-in thermometer.

As CPU temperature approaches a critical valve, above which CPU circuit damage could occur, the CPU protects itself by shutting down the entire system.

The temperature of a CPU chip is a function of the computing load it is handling. The more "work" the CPU is doing over an extended period of time, the hotter it will become.

Poor CPU cooling can be due to: poor air circulation around CPU cooling fan(s); cooling fan clogged or choked with debris; cooling fan not turning or poor thermal transfer between top of CPU and cooling fan assembly.

Solving random system shutdowns:

The design of many laptops has the cooling fan on the bottom. In many situations, raising the laptop up off the desk only a half inch or more will allow for better air circulation around the fans. Staples and other stores sell a laptop riser.

Laptops do not like their vents blocked and so using a laptop in your lap is a sure way to cause the laptop to overheat and shutdown.

With system powered on, observe cooling fan mounted on CPU chip. Is it turning? If it is not turning, it must be replaced.

If cooling fan on CPU chip is turning, is it clogged with debris? If so, you can use a can or 2 of compressed air to clean the fan blades and heat sink fins. If a laptop, also clean the air intake and heat out vents.

If the fan(s) on the CPU are turning and clean and the system is still randomly shutting itself down, then the thermal paste between the metal top of the CPU chip and the cooling fan that enhances heat transfer from the CPU to the cooling fan must be renewed. If you have to pay for this, probably one hour of tech time. It can be done do-it-yourself (DIY) but how you remove the cooling fan from the CPU, varies from system to system.