Computer Repair Tips

Computer Repair Tips

Sep 26, 2011

Fix Laptop Overheating Shutdown Problem 

Overheating and related shutdown problems are very common in laptops, especially in home use.  Common symptoms include some or all from this list;
– Laptop is extremely hot to the touch, especially around the fan area
– Fan seems to be running constantly, and at high speed
– Laptop shuts off by itself when doing nothing
– Laptop shuts off when playing games
– These heating or shutdown problems become worse over time, rather than getting better.

In around 1 in 10 cases, there is a fault with the cooling hardware. By this I mean either a mechanical failure with the fan where it can no longer spin, or spins slowly, or a motherboard electrical fault which exhibits itself by not telling the fan to spin fast enough to cool the laptop.

However 9 out of 10 cases of overheating are caused by an airflow blockage. In these cases, the fan is spinning as fast as it can, but if the hot air is obstructed from reaching the outside world, a heat build-up occurs and the laptop takes the safety precaution of turning itself off, rather than allowing permenant damage to occur.

I will, very quickly, explain how a laptop cools itself. Heat from the CPU, and sometimes the graphics chip, is conducted away from the processors via strips of copper metal. At the far end of this copper heatsink, the heat is fed into a series of side-by-side metal fins. This grill provides a very large surface area for the heat to be spread over. A fan then draws air from the outside world and blows across the hot grill, back towards the outside. As it does so, the air picks up heat from the hot metal fins and takes it away from the laptop.

Picture of a dust obstructed laptop heatsink finsIn an airflow obstruction scenario, the most likely culprit is a build-up of material in front of the metal heatsink grill. The fan will be drawing in cool air through vents from the outside world and occasionally there might be a tiny piece of fluff, hair or dust sucked into the laptop. When this air is being blown across the metal grill, the airborne material gets stuck on the front of the fins. If this keeps happening over time, gradually more and more material will build up on the front of the grill, creating an obstruction.

A common example of this buildup of material is shown in the image to the left.  All of the grey material is a combination of dust, lint, hair or fluff, compacted on to the front of the heatsink grill.

The effect of this is to block some of the airflow over the heatsink grill. With less physical space for the air to get through, the air is not picking up heat from the whole set of fins. So a smaller amount of heat is transferred to the air in it’s journey to the outside world. With less heat being removed, the heat starts to build up inside the laptop. Temperature sensors detect this and will react by making the fan spin faster and faster. The point of spinning the fan faster is to force more air through the available gaps, and past the hot metal fins to pick up more heat.

This compensation of spinning the fan faster can work to an extent, but eventually a limit will be reached. If the heatsink grill is sufficiently blocked, the fan will be spinning at maximum speed and it will no longer be possible to reduce, or even stabilse, the internal temperature of the laptop. Temperature sensors will realise this and as a final failsafe protection measure the laptop will power itself off. The hope behind this is that if the CPU is no longer producing more and more heat, the existing internal heat will gradually dissipate of it’s own accord and the laptop will, hopefully, avoid serious damage.

Laptop Fan with Screws Circled

Dell Vostro 3700 Heatsink Fan AssemblyTo fix this problem, you need to strip the laptop down to allow access to the heatsink and fan(s).  I’m not going to explain how to strip down a laptop, step by step, as there are guides elsewhere for this, and some manufacturers, for example Dell, even provide Service Manuals on the support pages of their website.

In most cases, to disassemble a laptop, all you will need are one or two small screwdrivers.  Some laptops require special torx screwdriver heads to remove some of the internal screws, so you will need to investigate this in relation to your particular laptop make and model.

The pictures I have taken for this post were from an overheating Dell Vostro 3700 laptop.  It would shut itself off after about 15 minutes of average use.  It was extremely hot to the touch around the fan area, and the overheating problem had gotten progressively worse over time.  The Dell Service Manuals explained how to remove the heatsink / fan assembly.

In this laptop, the fan was mounted on to a plate so I removed the screws holding the fan.  I’ve circled the tiny screws for easy identification.

The top image in this post shows the build-up of dust on the front of the heatsink fins.  In fact, it also goes to show that you don’t need a massive wad of dust to cause overheating and shutdowns.  In this case there was approximately 90% of the fins obstructed by a thin layer of material, but you can also see that there are still a few small gaps where a little air will have been able to pass through.  Each make and model of laptop will have it’s own threshold as to how much obstruction there can be before it causes a problem.  I’ve seen cases where there is a large solid strip of dust and fluff, several millimeters thick, that peeled away in one large piece.

After brushing away most of the dust build-up, I gave the heatsink fins and the fan a good blast with compressed air.  This blew away the last remnants of dust, and left a nice clean shiny heatsink grill and fan.

All that remained was to reassemble the laptop using the same steps as before, except in reverse.

The laptop is now working well and no longer overheats or shuts off by itself.  A side-benefit of this fix is that the laptop now runs a lot quieter.  Because the fan can now remove the excess heat in the laptop while running at a slower speed, it reduces the fan noise.  The laptop is also now a lot cooler to the touch.

 

 

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