Hot computers are slow and dangerous—here's how to fix yours

How hot is too hot?

man using laptop in bed
One easy way to make your computer overheat: Use it on a bed, where the blankets prevent airflow.Depositphotos

Ever feel like your laptop is about to burn your thighs? Or that the fan is spinning so loudly that it sounds like a wind tunnel? Running at high temperatures can permanently damage the computer. Here’s how to detect whether your PC is too hot—and make it chill out.

Thanks to the second law of thermodynamics, the electricity in your computer generates heat. Unfortunately, that warmth can damage the same components that produce it. That's why most computers keep their temperatures down with metal heatsinks, fans, and vents. But if something blocks the ventilation, a fan breaks, or cooling doesn't kick in properly, your machine will start to experience the signs of overheating.

Sometimes, the overworked computer will just slow down, because modern processors and graphics chips will “thermal throttle” themselves if the heat gets too high. If they force themselves to run at lower speeds, they’ll generate less heat and avoid more serious problems.

When techniques like throttling down and spinning the fans at full blast don’t help, the computer shuts itself down before the central processing unit (CPU) reaches dangerous temperatures. However, in some cases—particularly in older or poorly-manufactured machines—that heat can still damage certain parts of the motherboard before it automatically turns off.

"We've seen this many times," says Joe Silverman, owner of tech repair company New York Computer Help. "Sometimes the motherboard will get hot to the point where components can melt or snap off, which could cause the computer to totally stop working."

If you suspect your computer has been overheating—maybe it’s shutting down randomly, or frequently becoming too hot to handle (literally)—here’s how to diagnose and fix the problem.

How to check your computer's temperature

Heat isn't the only cause of slowdowns and shutdowns. Your computer could be failing for other reasons, such as a software problem. Thankfully, it's pretty easy to tell whether heat is the real culprit.

“If you turn on the computer and it turns off by itself a few minutes later, without opening any programs, that could be a problem,” says Silverman. You may also notice extra heat when doing something intensive, like playing games. If you’re still not sure whether your PC has been overheating, an app can check for you. (Note: These programs all use temperature units of degrees Celsius.)

For Windows, Speccy is the most user-friendly option, since it's super easy to read. Just install it and start it up. After that, it'll take a moment to check the temperatures of your CPU, motherboard, and GPU, indicating particularly hot components in red.

Mac users can download Macs Fan Control to see system temperatures. However, I would avoid using this app to actually control your fans unless you really know what you're doing. Download the program to check temperatures, but leave the fan settings on "Auto."

Once you choose an app, download it and leave it open in the background. When you experience a slowdown, shutdown, or other issue, check the temperatures—specifically the CPU and GPU values—to see whether they’re abnormally high.

“Typically, anywhere up to 70°C [158°F] is okay, but if it gets hotter, you might start having problems,” says Silverman. Your CPU and GPU will usually start throttling themselves between 90°C and 105°C (that’s 194°F to 221°F), depending on the model. And if you see temperatures that fall to negative levels or rise over 110°C (230°F), those numbers are wrong—this means your heat sensor is probably broken or the program doesn’t support it.

If the temperature does seem to spike at the same time you experience problems, then it’s probably safe to blame heat for your issue.

What to do if your machine overheats

Once you determine that your computer is, in fact, overheating, you need to figure out why. Here are a few of the most common culprits, and how to fix them.

  • Make sure the fan is running. "If it didn't run hot at first, and it's running hot now," says Silverman, "put your hand near the fan grille and feel for vibration, to see if the fan is working." If your fan is broken, then it won't dissipate that heat. You'll need to contact a professional who can replace it.
  • Blow out the dust. "Dust bunnies, debris, and food fragments can find their way through ducts and magnify the situation," says Silverman. He recommends grabbing a can of compressed air and using it to clean out the fan grille. "Try to angle the nozzle so you're blowing air out of the laptop." Cleaning out the gunk will allow the fan to run freely once more.
  • Check your surroundings. If something is blocking the airflow around your laptop, that could be causing your problem. "Don't put it on a bed—that's the worst thing you can do," says Silverman. "The blankets just stifle the airway. Put it on a flat desk, or on top of a flat book so air can flow." Some clamshell cases also stifle airflow, so if you have a case on the bottom of your laptop, try removing it. Other surroundings also matter: If the weather is hotter than 95°F, don't use your computer outside of the air conditioning.
  • Stick to a genuine battery and AC adapter. "If you replace your battery with a secondhand battery from Ebay or Amazon, you're going to have issues," says Silverman. "They aren't packaged the same way as the originals, so the heat tends to run hotter on the contacts. Don't skimp on the battery. Bad things will happen."
  • Update your software. This is rare, but occasionally, software and firmware issues can cause overheating. In fact, this just happened with Apple's latest MacBooks: They thermal throttled under seemingly-normal conditions until a recent software update fixed the issue.

If none of those suggestions seem to describe your situation, or the described fixes don’t help, you have two options: Open up your computer or call in the professionals. We recommend the latter solution. A repair shop can do a more thorough cleaning with specialized tools, and an expert might be able to diagnose other, more specific, hardware issues.